# Blown Engine Causes



## Ian Ariens 924 (Dec 22, 2015)

Start of the season here in Ontario 

I have bought many snowblowers with Tecumseh engines with broken connecting rods.

Question is what’s the major cause ?

My 3 bets are over reving , low oil or hitting something hard at full engine speed.

What are your thoughts ?


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## tadawson (Jan 3, 2018)

Wear and age . . . they aren't exactly young any more. The factors you list certainly can't have helped either.


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## ST1100A (Feb 7, 2015)

Most of what you listed is a cause, and Tecumseh was noted for connecting rod failure due to weak rods from manufacture, they were just not built strong enough for normal use in the first place. Mini bike usage where a lot of times the engines were over-revved and lubrication sloshing around caused very many failures on their engines, but they were not expensive to replace back in the 70's.


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## crazzywolfie (Jun 2, 2014)

i would say over revving from a sticky throttle or low oil would likely be the biggest reasons for them to blow up. i know i have dealt with quite a few machines where the throttle for some reason sticks. you can free it up and lube it but it eventually does it again. i know it was part of why i sold off my old snowblower. every year i had to free up the throttle again.


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## ST1100A (Feb 7, 2015)

C.W.
Yes the throttle and governor weren't the greatest back then.
I forgot to mention, there were a lot of aftermarket companies that made heavy duty connecting rods back in the 70's and 80's for them and they were not expensive, but put the rod in first before you blew it up.
Mini-bike and go-kart usage and failures were common back in the day, but those little Tecumseh's were a lot of fun for them back then, and easy to over-rev. If you blew one up, you went down to the local hardware store and got another one, and away you went, till you blew that one up. At least they were cheap to buy new back then.


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## JLawrence08648 (Jan 15, 2017)

Over revving. It's recommended to run at 3,600 rpm. I run at 3,450. But it may not mean much.


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## 1132le (Feb 23, 2017)

Not over revving I've run MANY they all have been run from 3750 to 3825 with no issues
clean full oil is they key I run them 1/16 over full checked and maintain before every use 45 yrs of doing this
lost 1 engine as gov took a crap and reved to 6k pop


1 useless stoopid owner low oil no oil
2 wear age
3 useless owner never change oil


over revving is a bs myth


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## 1132le (Feb 23, 2017)

ST1100A said:


> Most of what you listed is a cause, and Tecumseh was noted for connecting rod failure due to weak rods from manufacture, they were just not built strong enough for normal use in the first place. Mini bike usage where a lot of times the engines were over-revved and lubrication sloshing around caused very many failures on their engines, but they were not expensive to replace back in the 70's.



Weak rods what a joke 

they are 40 yrs old and still running most abused by stoopid owners
this how bs myths keep going you typed it therefore it must be true


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## Oneacer (Jan 3, 2011)

I have to go with 1132 on this topic.

*Owner Neglect … plain and simple* .. wrong oil (LOL, like 30W), bad oil or no oil at all. I suppose if someone neglected it to the point of no limit on the governor, well, surely the outcome would be catastrophic.

I never heard of Tecumseh noted for bad rods, and I have many from waaaayyyy back … they run great to this day, and of course, properly maintained, and that includes currently running the 5W30 *Full Synthetic* in all my equipment, new and old, summer and winter.


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## orangputeh (Nov 24, 2016)

have received 2 blown Honda engines in last 3 years. no or little oil in crank.
Honda dealer told me they get at least one blown engine a month. low or no oil is the cause. 

these machines don't have much of an oil capacity in the first place. 1.16 quarts in the bigger machines and 0.63 to 0.79 quarts in the smaller ones. no much room for error.


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## cranman (Jan 23, 2016)

Two years ago I sold a MTD blower to an older gentleman with an 8 hp Tec that I had serviced.....full oil (5/20 synthetic) governor adjusted to 3500 ...a nice solid running machine....He called me after using it for 20 minutes with a blown engine. No apparent reason for it lunching, so I replaced the engine for zip. Sometimes you got to suck it up.


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## Oneacer (Jan 3, 2011)

Just because you have an engine running, if you do not know where or how it was maintained over the years, you really have no idea of its condition or longevity. Never mind what the years of wear have left the internals.


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## crazzywolfie (Jun 2, 2014)

yup i freed up an engine for a buddy that he had ran low on oil. a couple weeks later the connecting rod came out the side of the block. i freed up an engine on a snowblower that i gave to my sister and it has been running good since. you definitely never know a engines history and it is always a gamble.


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## Ian Ariens 924 (Dec 22, 2015)

When I sell a blower, first thing I tell new owner ito do before blowing is to
Check oil level


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## Big Ed (Feb 10, 2013)

A lot of machines come with the oil in it already, I was told the main reason for this is because new owners would forget to add the oil.
I was looking for a belt for an old lawnmower I had,I was going around to shops in the area. One shop was owned by a Big Harley type of guy.
There was a customer who looked like Clark Kent who had just purchased another new mower. The old (new) one he blew up as he forgot to add oil.
He was trying to schedule a service appointment for it's first oil change. 
The Big guy was trying to explain that all you have to do is take off the oil plug and empty the oil then just pour in a jug.
He was trying his best to tell the guy how easy it was. But the guy said that he didn't trust himself to do it. 
The Big guy said that he had a minimum charge of $45 bucks an hour to do it. 
The guy made an appointment anyway.
After the guy left he looked at me and said do you believe that? I said yes.
I told him I would change oil all day long for 45 bucks. lol
He said 75% of his customers are like that, and he tries his best to save them money for something like that.
He feels guilty about taking their money for something so simple.
I told him not to. ha ha ha
He didn't have the belt I needed either.


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## HCBPH (Mar 8, 2011)

I agree things like over-reving, low oil are causes of engine failure. Because the engines are older, they can also be subject to material failure IMO, most being the 7 hp to 10 hp Tecumseh's. I can speak to the last one as it happened to me personally. The other year I serviced the Searasaurus which had a 10 HP Tecumseh on it. It was well maintained, oil up to proper level and checked. I started it up and let it idle may a minute or so after the choke comes up to get it up to normal range. While sitting there at 1/4 - 1/3 throttle there was a big bang and a hole in the block. Wanting to know what happened, I took it all apart. Bolts on the connecting rod were tight, oil was up to level and it hadn't been over-reved and I found no visible reason for the failure. It just looked like the connecting rod gave up the ghost, breaking the connecting rod and damaging the crank plus holing the block. I suppose that's why when rebuilding a automobile engine they magnaflux various parts including connecting rods looking for cracks etc.
In my case, I stripped off all the good parts and found another 10 HP Tecumseh which needed some minor modifications and fit it to the blower.


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## Nanook12 (Nov 26, 2019)

Yes a splash oil system needs lots of oil to splash around! Keep it just below the hydraulic-lock level. Also the oil pour point in cold weather is critical in a splash system. You can’t just let the metal parts grind together while waiting for the too thick of oil to warm up and start lubricating...


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## Oneacer (Jan 3, 2011)

That is why you use the 5W30 *Full Synthetic* oil, not just any oil, as many people do … 

You can have someone screw it up with the oil, ..... next year you may see nice, clean, proper oil, right level, fire it up … then "bang", Once you do damage, its there and can not be undone, and most likely will come back to bite you at some future point.


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## crazzywolfie (Jun 2, 2014)

Big Ed said:


> I told him I would change oil all day long for 45 bucks. lol


i would too lol. most of the time i usually charge $30 to do an oil change on most machines. $20 for my labor/base charge and $10 to supply the oil. if they supply the oil i will do it for the $20 but most of the time people don't have the oil or even know what to get. i have even been finding a lot more people overfilling the oil in there machine. not so bad with horizontal shaft engines but definitely a bit worse for the vertical shaft engines. 

i don't know if it would help with the keeping an engine from blowing but i have been starting to use motorkote in some of my machines. haven't got it in my snowblower yet but i know i started using it in some other equipment.


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## Ian Ariens 924 (Dec 22, 2015)

Picked up a Tecumseh 10 hp on a rusty MTD today.Bought it for the motor, it’s one of those twin output jobs.
Anyway I started it, runs good, so I bring it home 
I checked the oil, it is black.
So, warm it up a couple minutes, shut off ,undo the oil drain.
Water for first cup or so, then the oil.
Hope this motor survives


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## Oneacer (Jan 3, 2011)

Fingers X …….


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## crazzywolfie (Jun 2, 2014)

Ian Ariens 924 said:


> Water for first cup or so, then the oil.
> Hope this motor survives


i think the bigger determining factor is whether the connecting rod end was sitting in the water or not. i would say it has a 50/50 chance of surviving. it is stuff like this which has made me consider running motorkote in my small engines. i have seen a few engines over the years with water or ice in the engine and occasionally water in the crankcase. i guess if you really don't have a place to keep your machine out of the weather there is always the chance water may get into it and most of the time it seems like it may enter through the muffler.


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