# Tecumseh OHSK110 connecting rod damage



## ROTAC (Mar 1, 2021)

I have a seized OHSK110 Tecumseh engine off an Ariens ST1132le snowblower. I've got it apart and the connecting rod has broken and put a ding in the side of the block. Not cracked but almost. This is the second Tecumseh that I've seen this happen to. The other was an 8hp L head. What can be done to prevent this from happening? *I had one person tell me that when stored over the summer, ensure the piston is in the down position so the bottom of the connecting rod is in the oil* but is there anything else that should be done to prevent this. Between my sons and I we have three snowblowers with OHV Tecumseh engines. I plan on replacing the connecting rod in the above OHSK110. Just sourcing the part but I want to make sure I can prevent this from happening again. I may start adding a little LUCAS oil treatment to the 5W30 full synthetic oil. Any suggestions would be helpful as these are great engines and I want to keep them running as both the Ariens and JD snowblowers are bullet proof.


----------



## nwcove (Mar 2, 2015)

Get a rod designed for performance. ( look to the carting world).


----------



## 140278 (Aug 27, 2020)

most all single cylinder OPE engines are splash oiled or semi splash where like in kawasaki fj models a oil pump feeds the mains but they remain splash oiled on the con rods 
some of our members will tell you to install one of the very pricy forged/billet con rods, they are still splash oiled , while they don't break as easy, they can still seize to the crank.

real world we need to factor the age of many of these machines, metal fatigue. lack of maintenance by former owners, fact that these motors were designed to run about 200 hours before the above kick in.

what can be done? not much, before starting after sitting over the long down time between seasons, slowly turn them over with the pull starter before turning on the key to help splash some oil into the con rod helps, thick additives not me! just 5 w30 oil !


----------



## 3vanman (Nov 21, 2017)

captchas said:


> real world we need to factor the age of many of these machines, metal fatigue. lack of maintenance by former owners, fact that these motors were designed to run about 200 hours before the above kick in.
> 
> what can be done? not much, before starting after sitting over the long down time between seasons, slowly turn them over with the pull starter before turning on the key to help splash some oil into the con rod helps, thick additives not me! just 5 w30 oil !


Did you investigate further to determine what caused the connecting rod failure? 
Was the oil changed regularly" Was a 5w30 oil used?
Were you operating the machine in question when it happened? Or is this a motor you got on a machine?
As captchas points out, Tecumseh engines have stood the test of time. Many are 20+ years old, used in some of the worst weather conditions, started cold at -20, and then turned off when done and forgotten about until the next snow fall.


----------



## ChrisJ (Nov 27, 2014)

@captchas What's the 200 hour mark? Is that the expected life?! I've been curious how long the typical aluminum bore engine as well as how long the cast iron bore was expected to last? The 1960s Military engines we have laying around at work I believe claimed to be 1000 hour engines, but I have nothing to compare that to. How long is a Honda GX series expected to run?


----------



## Dusty (Dec 13, 2018)

I'm not sure where he got 200 hours from. 200 hours is just getting broken in for total life expectancy for one of those engines. I know for a fact, my 8hp Tecumseh on the Snapper I used had 1200 commercial hours on it when I sold it. At 1200 hours, the exhaust valve was out of spec and had to be corrected. Also the head bolt nearest the muffler stretched and took out the aluminum threads in that bolt hole. A larger bolt had to be obtained and that bolt hole had to be enlarged and the threads re-tapped for the head to seal properly. After that it ran fine again and its loss in power was regained. I know we didn't do anything special to that engine. We worked the snot out of it and many winters we stored it away exactly how it was after the last snowstorm when we rolled it off the truck. I'm sure the oil was changed far less than the suggested intervals too and we still didn't throw a rod. I hear when those engines throw a rod and they weren't neglected, it's just hit or miss, some get lucky, some don't. As far as the 200 hours, he may be talking about the environmental clean running rating, on what the engine is rated to run at, as far as the epa standard it was set at, which may be 200 hours, but that is not, the total life expectancy hour range for one of those engines. 200 hours is just getting broken in. Best thing you can do is take care of your engines and keep backups on the shelves now for the future in case one does blow, since they aren't making any more of these engines. They can still be found all over the place on used snowblowers cheap right now.
As far as splash lube vs ones that have an oil pump, which no snowblower has an oil pump engine anyway, its nonsense. I work on power equipment for a living, I see far more of those new Briggs Oil pressure lubricated engines blown up after only about 5 years of use, vs the old splash lube flathead engines and early splash lube ohv engines. Those older splash lube engines fail at FAR less the rate the newer pressure lube ones do. The old splash lube are still out their working while these new pressure lubed engines are throwing rods, like its their job. Don't believe me, I'll show you a pile of blown ones sitting in my backyard, vs teo splash lube that letgo, only because oil level got to low, on the pressure lube, the majority had proper level of oil. No evidence to suggest those pressure lubed engines last any longer than the splash lube on a small engine, in fact I'm seeing the opposite. Especially if oil level is maintained at the proper level.


----------



## dman2 (Sep 22, 2019)

I agreed with @captcha on the more expensive connecting rods. They cost as much as the engine themselves, and aren't guarantee to stop failures. If they don't break, the will seize/damage, or something else will give up.

I would say lack of lubrication and over revving are the two main reasons for these engine failures. Not much about the design I think.

With splash lubricating, you have to be very careful with your engine oil level, how to start your engine up and use it etc.

Many people had good luck with Tecumseh engines, so you can't say they are bad engines. Also, they were one of the most widely used engines out there, so by now, you should see them retiring.

No preventions for me. Just maintenance and use properly. When it gives up, it is time for a new engine.


----------



## ChrisJ (Nov 27, 2014)

Dusty said:


> I'm not sure where he got 200 hours from. 200 hours is just getting broken in for total life expectancy for one of those engines. I know for a fact, my 8hp Tecumseh on the Snapper I used had 1200 commercial hours on it when I sold it. At 1200 hours, the exhaust valve was out of spec and had to be corrected. Also the head bolt nearest the muffler stretched and took out the aluminum threads in that bolt hole. A larger bolt had to be obtained and that bolt hole had to be enlarged and the threads re-tapped for the head to seal properly. After that it ran fine again and its loss in power was regained. I know we didn't do anything special to that engine. We worked the snot out of it and many winters we stored it away exactly how it was after the last snowstorm when we rolled it off the truck. I'm sure the oil was changed far less than the suggested intervals too and we still didn't throw a rod. I hear when those engines throw a rod and they weren't neglected, it's just hit or miss, some get lucky, some don't. As far as the 200 hours, he may be talking about the environmental clean running rating, on what the engine is rated to run at, as far as the epa standard it was set at, which may be 200 hours, but that is not, the total life expectancy hour range for one of those engines. 200 hours is just getting broken in. Best thing you can do is take care of your engines and keep backups on the shelves now for the future in case one does blow, since they aren't making any more of these engines. They can still be found all over the place on used snowblowers cheap right now.
> As far as splash lube vs ones that have an oil pump, which no snowblower has an oil pump engine anyway, its nonsense. I work on power equipment for a living, I see far more of those new Briggs Oil pressure lubricated engines blown up after only about 5 years of use, vs the old splash lube flathead engines and early splash lube ohv engines. Those older splash lube engines fail at FAR less the rate the newer pressure lube ones do. The old splash lube are still out their working while these new pressure lubed engines are throwing rods, like its their job. Don't believe me, I'll show you a pile of blown ones sitting in my backyard, vs teo splash lube that letgo, only because oil level got to low, on the pressure lube, the majority had proper level of oil. No evidence to suggest those pressure lubed engines last any longer than the splash lube on a small engine, in fact I'm seeing the opposite. Especially if oil level is maintained at the proper level.


How do your Predators compare to everything else in regards to failures and hours?


----------



## Rooskie (Feb 12, 2015)

ROTAC said:


> *I had one person tell me that when stored over the summer, ensure the piston is in the down position so the bottom of the connecting rod is in the oil*


Welcome to the Snowblower Forum!
Common Practice has been to store the motor with both valves closed so the combustion chamber is sealed.
This just adds,'..at the bottom of the power stroke.' Sounds like a good idea off hand.


----------



## drmerdp (Feb 9, 2014)

I think captchas is referring to the emissions rating. Which can vary from 20 hours to a few hundred hours depending on the engine.

Ive seen Honda GX engines with multiple thousands of hours on them. My father was a framer back in the day and I still have his wheelbarrow air compressor equipped with a gx160 that has at least 5,000 hours on it.

A buddy of mine has a predator 420cc engine on his truck mounted air compressor with close to 2000 hours on it so far. Clones are definitely comparable to Hondas but not equal to Honda.

As tecumsehs go, their valves go out of spec very quickly. That’s their biggest issue In my opinion. When ever a tecumseh blows up I attribute it to low oil, too much oil, or an over rev situation.


----------



## Auger1 (Dec 4, 2020)

I would never run those old engines on Synthetic oil. They were not clearanced or designed to use the stuff.


----------



## ChrisJ (Nov 27, 2014)

Auger1 said:


> I would never run those old engines on Synthetic oil. They were not clearanced or designed to use the stuff.


I run Mobil 1 extended performance 5w30 in all of my small engines. This started because I run it in my cars and have extra.
I'm not sure why you're concerned about clearances when 5w30 meets the original viscosity requirements.


----------



## 3vanman (Nov 21, 2017)

Auger1 said:


> I would never run those old engines on Synthetic oil. They were not clearanced or designed to use the stuff.


Auger1, other than maintaining a better viscosity in cold weather, why would any engine not be designed to run on a synthetic oil that meets or exceeds the API standards for that engine? 
According to Tecumseh, synthetic oil is acceptable. "4. Can I use synthetic oil in my TecumsehPower engine?


> Yes you can. We recommend changing the oil after the initial two-hour break-in period. However, due to the price of synthetic oil it may be cost-effective to use a petroleum-based oil for this break-in period and use synthetic oil from then on. Click on the link below for further details."


Also, this you might find this an interesting read: Frequently Asked Questions


----------



## ST1100A (Feb 7, 2015)

ChrisJ said:


> @captchas What's the 200 hour mark? Is that the expected life?! I've been curious how long the typical aluminum bore engine as well as how long the cast iron bore was expected to last? The 1960s Military engines we have laying around at work I believe claimed to be 1000 hour engines, but I have nothing to compare that to. How long is a Honda GX series expected to run?


The Honda 'GX' series engines are given an 'Average Useful Service Life' of 2000 engine hours by the manufacturer. That means on average the engine should last for over 2000 engine hours without any serious wear and breakdown issues.
Your Tecumseh engines were given a 500 engine hour average useful service life expectancy by the manufacturer.
The standard Briggs engines were given 500 hours, their 'Industrial-Commercial engines were given a 1000 hour life.
Your Kawasaki and Yamaha engines were given 1500-2000 hour life.
A lot of your Honda 'Clone engines', or 'Discount' engines are given a 200-500 hour life, and some of the 'Clone' engines are not given any engine service life at all yet because they are too new and keep changing who and where they are made at, like a lot of the 'Fly by Night' companies that make the discount Clone engines.


----------



## ST1100A (Feb 7, 2015)

Auger1 said:


> I would never run those old engines on Synthetic oil. They were not clearanced or designed to use the stuff.


All engines made today are designed to run on 'Synthetic' oils or 'Standard' based oils, there is absolutely no difference there.
The clearance issues, the synthetic oils perform much better with clearance issues than a standard oil will.
Synthetic oils are made from petroleum oil base stocks and refined much much better and 'pureified' much better than 'Standard' oils.
That is why they are more expensive to purchase, they are of a higher grade which will withstand the extreme conditions better than standard oils.


----------



## ChrisJ (Nov 27, 2014)

ST1100A said:


> All engines made today are designed to run on 'Synthetic' oils or 'Standard' based oils, there is absolutely no difference there.
> The clearance issues, the synthetic oils perform much better with clearance issues than a standard oil will.
> Synthetic oils are made from petroleum oil base stocks and refined much much better and 'pureified' much better than 'Standard' oils.
> That is why they are more expensive to purchase, they are of a higher grade which will withstand the extreme conditions better than standard oils.


Thank you for the awesome reply regarding expected life. The cast iron bore Tecumseh's also only expected 500 hours? How do the iron bore compared to aluminum bore engines?

Wonder if it would be unreasonable to expect most Predator engines to last 2000 hours since they seem to be awfully good copies of the GX series?

Regarding synthetic oils and snow blowers, don't they also cope with moisture much better than conventional oils as well? BTW, I was also running synthetic in a 1931 Model A. I've yet to see any engine actually have a problem with modern synthetic oil.


----------



## ST1100A (Feb 7, 2015)

The Honda 'GC' series overhead camshaft engine is given a 500 hour engine service life, they were built to be compatible with the 'homeowner' Briggs, Tecumseh' and 'Clone' engines like the 'Predator' engines.


----------



## ST1100A (Feb 7, 2015)

ChrisJ said:


> Thank you for the awesome reply regarding expected life. The cast iron bore Tecumseh's also only expected 500 hours? How do the iron bore compared to aluminum bore engines?
> 
> Wonder if it would be unreasonable to expect most Predator engines to last 2000 hours since they seem to be awfully good copies of the GX series?
> 
> Regarding synthetic oils and snow blowers, don't they also cope with moisture much better than conventional oils as well? BTW, I was also running synthetic in a 1931 Model A. I've yet to see any engine actually have a problem with modern synthetic oil.


Most of your synthetic oils cope with moisture better than a standard oil will.
On your 'Iron' or 'Steel' bore engines, the cylinder walls will last longer than an Aluminum bore will.
A lot of your Aluminum bore engines built today have a special coating on them to make them last longer than the old ones did.
'Nikasil' plating which is a Nickel-Silicon' coating reduces ring friction and wear because it is harder and more slippery than the base Aluminum or Steel/Iron. It is also lighter in weight than a Steel 'Sleeve' in the Aluminum block.
Most of those engines with the special bore coatings, you cannot 'Re-Bore' the cylinder because you will remove the 'Coating'.
Other parts wear faster on the cheaper engines than the high hour engines will.


----------



## ChrisJ (Nov 27, 2014)

ST1100A said:


> Most of your synthetic oils cope with moisture better than a standard oil will.
> On your 'Iron' or 'Steel' bore engines, the cylinder walls will last longer than an Aluminum bore will.
> A lot of your Aluminum bore engines built today have a special coating on them to make them last longer than the old ones did.
> 'Nikasil' plating which is a Nickel-Silicon' coating reduces ring friction and wear because it is harder and more slippery than the base Aluminum or Steel/Iron. It is also lighter in weight than a Steel 'Sleeve' in the Aluminum block.
> ...



I'm sorry, last question...
Any idea how many hours Tecumseh HMSK's usually end up with exhaust valve issues I.E. not enough clearance due to seat wear?


----------



## ST1100A (Feb 7, 2015)

ChrisJ said:


> I'm sorry, last question...
> Any idea how many hours Tecumseh HMSK's usually end up with exhaust valve issues I.E. not enough clearance due to seat wear?


Hard to say on that. It varies a lot depending on how engine was taken care of.
Usually it is the valve face wear that causes the tight clearance not the seat wear.
valves wear faster than the seat. Seats can come loose if engine is overheated. Have to keep the cooling fins clean from debris.
The wear can happen within a couple hundred hours or so.


----------



## ChrisJ (Nov 27, 2014)

ST1100A said:


> Hard to say on that. It varies a lot depending on how engine was taken care of.
> Usually it is the valve face wear that causes the tight clearance not the seat wear.
> valves wear faster than the seat. Seats can come loose if engine is overheated. Have to keep the cooling fins clean from debris.
> The wear can happen within a couple hundred hours or so.



Years ago someone I know had theorized the emissions carb running lean caused the wear.


----------



## ROTAC (Mar 1, 2021)

captchas said:


> most all single cylinder OPE engines are splash oiled or semi splash where like in kawasaki fj models a oil pump feeds the mains but they remain splash oiled on the con rods
> some of our members will tell you to install one of the very pricy forged/billet con rods, they are still splash oiled , while they don't break as easy, they can still seize to the crank.
> 
> real world we need to factor the age of many of these machines, metal fatigue. lack of maintenance by former owners, fact that these motors were designed to run about 200 hours before the above kick in.
> ...


Thanks for the info. I appreciate it.


----------



## ROTAC (Mar 1, 2021)

captchas said:


> most all single cylinder OPE engines are splash oiled or semi splash where like in kawasaki fj models a oil pump feeds the mains but they remain splash oiled on the con rods
> some of our members will tell you to install one of the very pricy forged/billet con rods, they are still splash oiled , while they don't break as easy, they can still seize to the crank.
> 
> real world we need to factor the age of many of these machines, metal fatigue. lack of maintenance by former owners, fact that these motors were designed to run about 200 hours before the above kick in.
> ...


The engine came on the Ariens when I bought it. It was seized but I got the whole machine for $50 so it was a chance buy and if I get the engine running again it will be well worth it. Unknown what oil was in it or for how long. But my guess is it was neglected. The rest of the machine is good and the motor doesn't look abused but like you say, hard to know what it's been through. Once it is back up and running I'll do what I can to look after her. I have several Tecumseh engines between 20 and 30 years old but haven't had this happen to any and they still fire right up and run well.


----------



## ST1100A (Feb 7, 2015)

ChrisJ said:


> Years ago someone I know had theorized the emissions carb running lean caused the wear.


No that wouldn't cause it. The leaner carbs were set to cut down on Hydro-carbon/un -burned fuel emissions. If anything, there was less carbon build-up caused by that plus a little better fuel mileage.
The valves are made of hardened steel and newer ones have the 'Stellite' coating on them, a 'Hard- Surface' compound to make the surface harder, but they do wear after being 'Hammered' in from opening and closing repeatedly over a period of time plus the heat they are subjected to softens the surface when it gets that hot.


----------



## ST1100A (Feb 7, 2015)

On most all engines the connecting rod never sits down in the oil so leaving the piston at bottom dead center wont let it set in the oil. The little 'Dipper' rod at the end of the connecting rod splashes down into the oil to splash it around the engine if it is lubed by the 'Splash' type. Pressurized lubrication works differently but you would have a lot of air bubbles in the oil if the crankshaft and connecting rod 'Big End' bearing hits the oil supply in the crankcase. It would also slow the engine down from the friction of hitting the oil while it is spinning/rotating.
If the crankshaft would constantly hit the oil all the time it would cause excessive oil consumption by 'aerating' it, causing it to 'Mist' and the mist would get sucked through the breather or leak out.
It would also cause a lot of air bubbles in the oil so it would not lubricate its surfaces properly, you wouldn't have a solid film of oil, you would have a lot of 'Air Spots' in the oil film, causing metal to metal contact and ruin whatever the oil is trying to keep apart.


----------



## ChrisJ (Nov 27, 2014)

ST1100A said:


> On most all engines the connecting rod never sits down in the oil so leaving the piston at bottom dead center wont let it set in the oil. The little 'Dipper' rod at the end of the connecting rod splashes down into the oil to splash it around the engine if it is lubed by the 'Splash' type. Pressurized lubrication works differently but you would have a lot of air bubbles in the oil if the crankshaft and connecting rod 'Big End' bearing hits the oil supply in the crankcase. It would also slow the engine down from the friction of hitting the oil while it is spinning/rotating.
> If the crankshaft would constantly hit the oil all the time it would cause excessive oil consumption by 'aerating' it, causing it to 'Mist' and the mist would get sucked through the breather or leak out.
> It would also cause a lot of air bubbles in the oil so it would not lubricate its surfaces properly, you wouldn't have a solid film of oil, you would have a lot of 'Air Spots' in the oil film, causing metal to metal contact and ruin whatever the oil is trying to keep apart.



I always thought the crank splashed down into the oil as well but then why would it need a dipper...

But then I have to ask, what's the huge difference between a wet sump engine and a dry sump if all that's touching the oil is the dipper? For that matter pressurized systems I don't think even have dippers yet they claim dry sump is much better?


----------



## 140278 (Aug 27, 2020)

Dry sump - Wikipedia







en.wikipedia.org


----------



## ChrisJ (Nov 27, 2014)

captchas said:


> Dry sump - Wikipedia
> 
> 
> 
> ...


I read that a few times.
I was under the impression wet sump engines had a lot more sloshing / splashing than they actually do.

After reading ST1100A's comment I went and looked at where the oil level would be vs the crankshaft and I'm amazed. I never realized that before and it makes sense, why would you need a dipper / slinger otherwise.

*I've learned a lot in this thread. I hope I can remember it.*


----------



## jr27236 (Feb 19, 2021)

I have rebuilt and worked on plenty of small motors from chainsaws to large OHV motors. The main reason these 4 stroke motors seize is because of poor to no lubrication. You can have a piston seizure where the piston starts seizeing in the cylinder and the connecting rod detonates or brakes just before the piston and punches holes is the case or you can have the connecting rod seize to the journal and shatter or a combo of both. Either way they are due to lube issues because of low to no oil in the case.
On any cold weather engine it is advised to start and let the engine warm at low rpm to operating temperature before increasing to wide open throttle. This lets the oil warm and properly lube the motor properly before creating heat/friction by running it WOT ice cold. This is especially advised on OHV motors. 
Shutting off the motor with the cylinder at the bottom of its stroke will not aid in anything. I write this based on my experience and observations in the engines I have repaired and pronounced DOA.


----------



## 140278 (Aug 27, 2020)

proper lubrication when cold is one of the many reasons OPE engine manufactures have oil/temp charts .with winter use of 5w30 on the older motors and recent motors 5w30 and 0w30 


IT's long been best to carefully read the owners manual about proper operation and oil recommendations


----------



## CarlB (Jan 2, 2011)

ChrisJ said:


> How do your Predators compare to everything else in regards to failures and hours?


I haven't heard of any predators throwing a rod.
I have had at least 6 of them and they all ran started and ran well.


----------



## jr27236 (Feb 19, 2021)

ChrisJ said:


> How do your Predators compare to everything else in regards to failures and hours?


My son and I put a predator 212 on his go cart. We kick the crap out of that thing. Even bi-passed the goveror and hold it WOT. The thing wont die! We tey to kill it every time lol! we recently tore a chain link in half after we lauched in the air out of a steep valley lol. Thing goes 38 MPH on a single wheel drive and my son weighs 230 plus the go cart weight. If this engine is an example of there quality, longevity I say get one.


----------



## laser3kw (Feb 11, 2018)

some good reading
Arc Billet rod for tec (link)
The company may have the upgrade rod for the OHV. I use to race karts and the 5 & 10hp Tecumseh flat heads were beasts! There was a nice after market of parts to hop up them and let them live.
Me, I'm a gearhead, I would do the same as you (OP). The biggest problem with the tec rods was light weight design and lack of a oil passage (like Briggs has)


----------



## ChrisJ (Nov 27, 2014)

laser3kw said:


> some good reading
> Arc Billet rod for tec (link)
> The company may have the upgrade rod for the OHV. I use to race karts and the 5 & 10hp Tecumseh flat heads were beasts! There was a nice after market of parts to hop up them and let them live.
> Me, I'm a gearhead, I would do the same as you (OP). The biggest problem with the tec rods was light weight design and lack of a oil passage (like Briggs has)


People "hop up" Tecumseh engines?


----------



## 140278 (Aug 27, 2020)

look up nhra jr dragster engines you will be very surprised at how far, while most are briggs based they do also use tech bases, billet blocks, heads,rods, steel stroker cranks. gas, methanol and nitro .prices on motors can run to 6 grand and better


----------



## laser3kw (Feb 11, 2018)

ChrisJ said:


> People "hop up" Tecumseh engines?


People will hop up anything!
My stock class legal Tec 5 with the "soda straw" carb (rules mandated - to keep power down) made 12.3 hp (on gas) on my dyno. I would twist it above 6000 rpm and it was bullet proof ( yes, it had a billet rod - legal per rules)!
The Tecumseh "Star" motor - 10hp flat heads - were into the mid 20's and touching 30 hp and maybe more.
here is a link to "hop up" parts that may fit many of the snow blower motor - Tech, B&S, Honda, Clone -
[Small engine performance parts link


----------



## ChrisJ (Nov 27, 2014)

captchas said:


> look up nhra jr dragster engines you will be very surprised at how far, while most are briggs based they do also use tech bases, billet blocks, heads,rods, steel stroker cranks. gas, methanol and nitro .prices on motors can run to 6 grand and better


I am very surprised.

Interesting. Maybe I'm 100% wrong when it comes to Tecumseh engines.


----------



## PhilThefarmer (Dec 21, 2020)

actually, sometime, the governor gear also act as an oil splasher, I know my b&s 11hp doesn't have one, so it has a dipper at the end of the connecting rod, but I don't think it is the same for all engine, L head or OHV head


----------



## jr27236 (Feb 19, 2021)

Thankfully I have never blown or seized a motor. I believe with proper maintainance and simply checking the oil level with prevent 99% of these failures.


----------



## Auger1 (Dec 4, 2020)

The problem is, the aluminum connecting rod period. When we race sbc's or bbc's I never use them because of the short cycle life of the aluminum rod and the as you put more runs on the engine you reach the fatigue life of the material pretty easy with aluminum. Years ago when I was a youngin we raced mini-bikes with the 5hp Tecumseh's and B&S engines. We would take out the gov. and run them to the moon and yes you guessed it, we busted the connecting rods on every one of them. About a year later someone at one at the local little engine shops came out with the steel connecting rod for the B&S engine so I bought one. We beat the snot out of that little 5hp, WOT all the time and it never broke a rod, so you see it's not the engines fault it the manufacture putting in the aluminum rod because when it reaches the cycle life of the material something gotta give.


----------



## jr27236 (Feb 19, 2021)

Auger1 said:


> The problem is, the aluminum connecting rod period. When we race sbc's or bbc's I never use them because of the short cycle life of the aluminum rod and the as you put more runs on the engine you reach the fatigue life of the material pretty easy with aluminum. Years ago when I was a youngin we raced mini-bikes with the 5hp Tecumseh's and B&S engines. We would take out the gov. and run them to the moon and yes you guessed it, we busted the connecting rods on every one of them. About a year later someone at one at the local little engine shops came out with the steel connecting rod for the B&S engine so I bought one. We beat the snot out of that little 5hp, WOT all the time and it never broke a rod, so you see it's not the engines fault it the manufacture putting in the aluminum rod because when it reaches the cycle life of the material something gotta give.


I currently have a 212 predator on my sons go cart. Gov removed and we kill (i ride it also lol) this this through trails. Im waiting to it to blow up but it wont. At least not yet that is.


----------



## 140278 (Aug 27, 2020)

another issue today is metal fatigue these motors are old,stress takes a toll , crack/break


----------



## 140278 (Aug 27, 2020)

jr27236 said:


> I currently have a 212 predator on my sons go cart. Gov removed and we kill (i ride it also lol) this this through trails. Im waiting to it to blow up but it wont. At least not yet that is.


hear that some of the nhra jt dragster motors are spinning out 30 plus hp with forged parts they hold up for a good 50 runs like my grandsons did running methanol


----------



## tadawson (Jan 3, 2018)

> The problem is, the aluminum connecting rod period. When we race sbc's or bbc's I never use them because of the short cycle life of the aluminum rod and the as you put more runs on the engine you reach the fatigue life of the material pretty easy with aluminum. Years ago when I was a youngin we raced mini-bikes with the 5hp Tecumseh's and B&S engines. We would take out the gov. and run them to the moon and yes you guessed it, we busted the connecting rods on every one of them. About a year later someone at one at the local little engine shops came out with the steel connecting rod for the B&S engine so I bought one. We beat the snot out of that little 5hp, WOT all the time and it never broke a rod, so you see it's not the engines fault it the manufacture putting in the aluminum rod because when it reaches the cycle life of the material something gotta give.


No, it's the end users fault for overreving it in those cases . . .


----------



## ChrisJ (Nov 27, 2014)

Here's something that's been on my mind for a while now.
The HMSK80 and HMSK100 and other variants have been used on snowblowers for years.
The HM80 and HM100, seem to have been used on generators. On a 2 pole 60Hz generator you'd adjust it to run around 3750-3800 rpm unloaded. This would give you closer to 3600 rpm at full load.

If all of those Tecumseh engines on generators had no problem running at 3750-3800 rpm unloaded why is it such a huge deal not to go over 3600 on a snowblower with the same basic engine?


----------



## tadawson (Jan 3, 2018)

You make the false assumption that folks leave generators running unloaded. I suspect most are running very close to 3600, as designed. Genny load is also likely a lot more steady state than a snownlower, which may also explain the higher "margin" on a blower.


----------



## ChrisJ (Nov 27, 2014)

tadawson said:


> You make the false assumption that folks leave generators running unloaded. I suspect most are running very close to 3600, as designed. Genny load is also likely a lot more steady state than a snownlower, which may also explain the higher "margin" on a blower.


That certainly doesn't describe the kind of use I've seen low end 4kw and 5kw generators used for.


----------



## Shovel (Mar 26, 2019)

Auger1 said:


> The problem is, the aluminum connecting rod period. When we race sbc's or bbc's I never use them because of the short cycle life of the aluminum rod and the as you put more runs on the engine you reach the fatigue life of the material pretty easy with aluminum. Years ago when I was a youngin we raced mini-bikes with the 5hp Tecumseh's and B&S engines. We would take out the gov. and run them to the moon and yes you guessed it, we busted the connecting rods on every one of them. About a year later someone at one at the local little engine shops came out with the steel connecting rod for the B&S engine so I bought one. We beat the snot out of that little 5hp, WOT all the time and it never broke a rod, so you see it's not the engines fault it the manufacture putting in the aluminum rod because when it reaches the cycle life of the material something gotta give.


Indeed..the rod breaks from the stress of changing direction at fast speed..a double of rpms shocks the rod with four times the energy.
The engines which share everything except a larger bore break the rod faster due to the heavier piston.
Granted larger engines may have beefier rods..but not always or it may not be enough...Add to the fact the quality of the rod itself can vary just from one batch to another..these small engines with the aluminum rods have no problems breaking the rod.
The lower displacement engines within the same family seem to live the longest as it hasn't been bored or stroked for more displacement yet.

Sent from my SM-A115U1 using Tapatalk


----------



## Shovel (Mar 26, 2019)

ChrisJ said:


> Here's something that's been on my mind for a while now.
> The HMSK80 and HMSK100 and other variants have been used on snowblowers for years.
> The HM80 and HM100, seem to have been used on generators. On a 2 pole 60Hz generator you'd adjust it to run around 3750-3800 rpm unloaded. This would give you closer to 3600 rpm at full load.
> 
> If all of those Tecumseh engines on generators had no problem running at 3750-3800 rpm unloaded why is it such a huge deal not to go over 3600 on a snowblower with the same basic engine?


Generators use the governor set with as low a droop as you can get them while the engine speed remains stable.
When a load is placed on an engine..a governor will lag at the governor momentarily...the same as when the load is released...the engine will overshoot its governed RPM momentarily then come back down.
Snowblowers use a different spring and or a different hole in the governor bracket..which allows more overshoot/under shoot(Less sensitivity)
Also to remember that much of the world use 50hz which puts a Generator at 3000 rpm under load.
We don't run 3750 no load because we can..its because we have to.
Let's take a no load of 3750 rpm..load the Generator..then release the load..the engine overshoots the 3750 and may touch 3900..maybe slightly more for a split second..
A Snowblower set to 3750 will overshoot further with the load released than the Generator...as the governor is not set as sensitive.
Generators have no problems breaking the rod..most of them don't retire from using oil but from busting the rod.
Also here in the states horsepower sells...3600 usually produces more power..In much of the world these engines are slowed down quite a bit for a longer engine life.
Here in the states alot of Toros are running 3300 3350 RPMs..MTD 3450 RPMs.
Reason being a longer engine life..since HP isn't usually stated anymore but rather max torque..which occurs at a much lower RPM..its the number people are looking at..So let's say we had an engine rated 8 hp at 3600 rpm..it really wasn't providing 8 hp any way as the carb isn't opening all the way until maybe 3200 rpm or so anyway..it will have produced 8 hp at 3600 wide open throttle..The Generator was the closest..as it was actually overspeeded then pulled back down to 3600 
When they stopped claiming HP on engines they started slowing them down as they will still have the claimed torque figure..usually between 2400 to 2800 rpms..longer engine life being the goal with reduced engine speed.




Sent from my SM-A115U1 using Tapatalk


----------



## ChrisJ (Nov 27, 2014)

Shovel said:


> Generators use the governor set with as low a droop as you can get them while the engine speed remains stable.
> When a load is placed on an engine..a governor will lag at the governor momentarily...the same as when the load is released...the engine will overshoot its governed RPM momentarily then come back down.
> Snowblowers use a different spring and or a different hole in the governor bracket..which allows more overshoot. (Less sensitivity)
> Also to remember that much of the world use 50hz which puts a Generator at 3000 rpm under load.
> ...



Ok that makes sense but then there's the other thing I've been curious about.

Why use a less sensitive governor on a snowblower if the one used on a generator doesn't hunt?

What would happen if an engine was taken from a generator and put on a snowblower (tapered shaft aside....)


----------



## Shovel (Mar 26, 2019)

ChrisJ said:


> Ok that makes sense but then there's the other thing I've been curious about.
> 
> Why use a less sensitive governor on a snowblower if the one used on a generator doesn't hunt?
> 
> What would happen if an engine was taken from a generator and put on a snowblower (tapered shaft aside....)


You have to have a perfect tune to stop a generator from hunting...or adjust the governor to 'just ' get rid of the hunting..
Its a comprise setting...ideally we want no droop but it's not possible with a mechanical governor. 
Sensitive governors on a snowblower would be having alot of warranty work required


On snowblowers and such..engine speed isn't as critical as the generator has to spin 3600 to keep the 60hz.
As long as we run our snowblower engine somewhat above peak torque RPM we are good.

You could run a generator engine on a snowblower ..yes..its gonna hunt for a while in the cold climate though..unless you put a load on it.

Sent from my SM-A115U1 using Tapatalk


----------



## ChrisJ (Nov 27, 2014)

Shovel said:


> You have to have a perfect tune to stop a generator from hunting...or adjust the governor to 'just ' get rid of the hunting..
> Its a comprise setting...ideally we want no droop but it's not possible with a mechanical governor.
> Sensitive governors on a snowblower would be having alot of warranty work required
> 
> ...


You bring up very good points I didn't think it.
I try to keep my equipment running as close to perfect as I can. I tend to forget that's not typical and warranty work would be a huge factor.

90% of the snowblowers and lawn mowers I hear around me are usually hunting and that's with a normal governor.


----------



## Shovel (Mar 26, 2019)

ChrisJ said:


> You bring up very good points I didn't think it.
> I try to keep my equipment running as close to perfect as I can. I tend to forget that's not typical and warranty work would be a huge factor.
> 
> 90% of the snowblowers and lawn mowers I hear around me are usually hunting and that's with a normal governor.


Alot of people set up a generator for the usual load they are going to use then set the speed...since they are running a lighter load they can decrease no load speed or sensitivity.
Alot of generators out there that just won't run no load 3750 and take a pull and stay above 3600..some speed em up a little and others try the get the governor set as sensitive as possible while remaining stable..then recheck..thats the proper way...Some equipment isn't frequency sensitive so taking the drop isn't an issue.
But as a general rule low frequency or voltage isn't good..but for lights or resistance heaters no big deal.
Some people run high on purpose as some electric motors really hit a generator hard while the electric motor spools up.
But yeah..I hear alot of equipment out there hunting as well..alot of the mowers etc have droop of around 12 to 15 percent and still hunt..its because it lean on the pilot circuit..while running full engine speed without a load ..the throttle is just barely open anyway and still relies heavily on the pilot circuit in the carb.
The orifices are so small they can clog off season with stale fuel..usually alcohol being the cause.

Sent from my SM-A115U1 using Tapatalk


----------



## jr27236 (Feb 19, 2021)

Shovel said:


> Alot of people set up a generator for the usual load they are going to use then set the speed...since they are running a lighter load that can decrease no load speed or sensitivity.
> Alot of generators out there that just won't run no load 3750 and take a pull and stay above 3600..some speed em up a little and others try the get the governor set as sensitive as possible while remaining stable..then recheck..thats the proper way...Some equipment isn't frequency sensitive so taking the drop isn't an issue.
> But as a general rule low frequency or voltage isn't good..but for lights or resistance heaters no big deal.
> Some run high on purpose as some electric motors really hit a generator hard while the electric motor spools up.
> ...


Hunting has nothing to do with the gov. Not to be insulting but where are you getting these points you are making? Carb, carb, carb causes hunting period. Governors prevent over reving. Yes you can mess with a gov to effect rpms. 
Also who is adjusting the rpms on there gen? The engine has to spin the gen head at the proper rpm to produce the proper 120volts and hz. I dont know who is messing with engine rpms to produce more or less electricity.
Generators are fully dependent on engine RPMS.


----------



## Shovel (Mar 26, 2019)

jr27236 said:


> Hunting has nothing to.do.with the gov. Not to be insulting but where are you getting these points you are making? Carb, carb, carb causes hunting period. Governors prevent over reving. Yes you can mess with a gov to effect rpms.
> Also who is adjusting the rpms on there gen? The engine has to spin the gen head at the proper rpm to.produce the proper 120volts and hz. I dont know who is messing with engine rpms to produce more or less electricity.
> Generators are fully dependent on engine RPMS.


Hunting is the governor trying to control engine speed..when the engine achieves set speed the governor pulls the throttle shut.
The spring pulls the throttle open..the governor pulls it shut when speed is achieved.
Example...place a small load on the engine and the throttle opens a little..apply a large load and it fully opens...release the load and the throttle returns back to barely open.
Engine speed is set by spring tension. 
As I stated earlier most hunting is caused by a clogged or partially clogged pilot circuit ..what happens is at full speed no load/ the throttle is barely cracked and still is reliant on the pilot circuit. 
A lean condition will cause the throttle to open back up when the throttle reaches the lean area in regard to throttle position/ 
Speed is reached...the governor reacts..closes throttle and the cycle continues. 

People adjust the engine generator speed to achieve the 3600 rpms 60hz under load..thats why the adjustment is there.
The speed is set higher so it pulls back to 3600 under load..if droop is to high then an adjustment of the governor is needed..if low droop can't be achieved then the carb needs cleaned.

Gov droop is adjusted by spring strength or hole placement..moving the spring further or closer to its pivot is the same as changing spring strength...a 'lighter' spring is a low droop spring but is more apt to hunt.

Speed is controlled by the throttle arm pulling the spring itself..the spring pulls the throttle open and the governor pulls it shut.
Due to friction...and the inertia of the governor components themselves..Zero droop is physically impossible. 

Sent from my SM-A115U1 using Tapatalk


----------



## ST1100A (Feb 7, 2015)

Good explanation Shovel. 
Electronics are very sensitive to frequency change and can be damaged easier by the change in it, also 'Timers' rely on frequency being steady.
Some of your more 'Top End' generators are now using electronic controlled governors to keep them very stable with even less governor 'Droop'.


----------



## ST1100A (Feb 7, 2015)

Connecting rod failure depending on where the failure starts at is from different causes normally.
Normally when it is a 'bearing' failure, that is usually caused by a lubrication problem but not always, 'Over-Revving' can also play a part in it along with Metal Fatigue. Metal Fatigue being less likely than lack of lubrication to the bearing.
Many rods break at the 'Beam'' the area between the crank bearing and the piston pin. A breakage there is more of a 'Metal Fatigue' failure which can be caused by 'Over-Revving' more so than a lubrication failure.
You have to trace and rule out lubrication failure first by inspecting the bearing surface to make sure there is no abnormal wear such as 'Ovaling of the bearing journal hole causing a 'Slap' shock in the rod.
The connecting rod is subject to a tremendous amount of 'Reciprocal' motion and force, 'Back and Forth' movement that suddenly changed direction which can cause a piece of metal to suddenly break apart if it is not strong enough or has any 'Fatigue' in it.
The older Tecumseh 'L'/Flathead engines were known for weak rods and failures when over-revved but back then they were inexpensive to repair or replace, and they did like to rev pretty high on go-karts and mini-bikes with governors disconnected or modified to over-rev easily.
In most of those cases where they were used on mini-bikes and go-karts, they also suffered lubrication failures because the engine was moving around, tilted and bounced a lot more, causing the oil to not be 'Splashed' properly to lubricate bearings.
The design and type of the carburetors used on the Tecumseh's were better for go-kart and mini-bike use because they could handle and deliver the fuel a lot better than the types of carburetors used on the Briggs engines at that time.
Some of you may remember back in the early 70's when you were younger you would go out after school before your parents got home from work and went out 'Racing' around with your 'Recreational' vehicles, driving on the streets 'illegally' then 'Off-Roading' them like you were 'Evil Knievel' and blowing the engines up frequently.
You would park the machine and run down to the local 'Hardware' store to buy a new engine with your saved 'Allowance' money from 'Mom and Dad' and buy a new engine to replace the one you blew up without your parents knowing what you did.
Then one day your Dad went out to the shed to get the lawnmower out and found a pile of 'Newer' engines that were 'Leaking' oil, what little bit of oil that was left in them with a nice big hole in the side of the block that you forgot to hide well enough so Dad wouldn't find it, then you had some 'Explaining to do' to your parents.


----------



## laser3kw (Feb 11, 2018)

speaking of rod failures....
ever see one like this?









Ponder that for awhile....


----------

