# Briggs "900" OHV No-Start, Tried Everything, Any Tricks With These Models?



## MDchanic (Jan 17, 2020)

Hello! 

I'm a new member with a problem that's driving me crazier than it needs to, seeing as how I've got another snow blower I can use.

Let me first say that I've been fixing motors since I was a kid (and that's over half a century) and I have never found myself unable to get an engine started, if it was possible for it to run at all.

The motor in question is a Briggs "900" series 205cc 1 cylinder, OHV snowblower motor from 2014, model number 12D105-0172-F8 with a build date of 4/15/14. 

It is in a snowblower that I bought from an elderly neighbor last month. He's a fairly straight shooter about these things, not a mechanical guy, told me he bought it, used it a few times, less than 8 hours total, and felt it was "too much for him," so he left it in his barn. Looking at it, in terms of rust, oil leakage at seals, wear on auger, etc., I have no reason to disbelieve him. 

I went over to his barn, unscrewed the bottom bolt on the float bowl, wiped out the crud, ran some gas out of the tank, put it back together, and it started right up. I ran it about 600' to my barn and it quit. It was getting dark, so I left it. Next day, I filled the tank with fresh gas, gave the float bowl and jet a better cleaning, and it started right up. I blew some snow for about half an hour, it ran well, then it quit.

After that, I could never get it to really even fire. 
It will crank faster and almost catch when I spray ether into the carb, but it never really catches, will "sound good" for only about 2-3 seconds after a spray of ether, then return to normal. It will not pop even once if I stop cranking it.

What I've done:


Checked spark - maybe a little too orange - hard to tell on a magneto 1-banger, so I installed a new B&S coil (with wire). No real change. Could be bad out of the box. Got another factory coil, still no change.

Replaced spark plug with a cheap one, on sale for $1! Looked a bit better. Still no change. 
Replaced with a fancy gold B&S plug. Still no change. 

Removed carb. Disassembled, blew out, reassembled. Still no change.

Removed flywheel, looked at key and keyway. Perfectly aligned. Retorqued (60 ft/lbs, right?).

Removed valve cover, set cylinder to TDC, rough feel for endplay is about 0.008" for both.
Confirmed both valves push down and move freely.
Removed 1 pushrod - Not bent. 
Rotated engine (on electric starter), watched valve & rocker movement, smooth and equal between the sides, no binding.

Bought new B&S carb, installed. No change. 

Motor has had good compression by feel on pull-starter and at spark plug hole throughout.

So, I feel I can say that:

Fire is good.
Air is good.
Fuel is good.
Compression is good.
Timing is good.
Valves are good.

Speed control is wide open, varying choke position doesn't matter, air screen on or off, shrouds on or off, kill switch connected or disconnected (same spark all the time anyway), fuel runs out freely when valve is open and either hose is disconnected or float bowl is off.

What the heck else is there???

Is there anything that fails on these after low use but long storage that I"m missing?

Aside from actually putting a compression gauge on it, is there anything I haven't done?

I'm at the point where I know it has to be something simple and obvious, but I can't for the life of me figure out what I haven't checked.

Anybody have any ideas?

The guy said he'd give me my $200 back, but at this point it's not about money - it's a matter of pride.

Thanks,

- Eric


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## Kiss4aFrog (Nov 3, 2013)

:welcome: to SBF Eric

It's not pride, you're on a mission from God now :grin:

I'd pull the plug, let the cylinder and plug dry out for an hour or two and then put it back in and try hitting it with starting fluid to see if it will pop.
If it does we go from there.

.


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## penna stogey (Nov 25, 2019)

Welcome to the SBF from Gettysburg...


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## MDchanic (Jan 17, 2020)

Hi Frog and Stogey.

Sorry for the late reply - I don't seem to be getting e-mails when there are responses. I'll have to manually subscribe.

Yes, I did remove the plug, air it out, etc. Did so several times. Left it open for several days. Used different plugs (unusual for me, I generally just clean the old plug with a wire brush and lacquer thinner).

The one thing I haven't done is to actually measure the valve lash (I put it at TDC and just felt for a normal amount of play), so some time in the next few days, I'll have to do that. The guide I saw said 0.005" intake / 0.010" exhaust, a couple of degrees past TDC, presumably with the engine cold. I doubt that's it, but I have to be able to say I confirmed it.

I'm at the "just walk away for a while" stage right now. Usually when I do this, something comes to me, but it hasn't yet.

Thanks,

- Eric


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## Motor City (Jan 6, 2014)

I would check compression, and if the cam skipped a tooth at this point. And as you are going to do, check the valve lash. If I recall, the piston should be 1/4in below TDC, to check lash.


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## Town (Jan 31, 2015)

There is a setting in your profile to allow e-mails for responses to your posts. Kiss4afrog let me know the setting. I will try to find it.

I went through much the same process on my son's 11hp Tecumseh OHV. It would fire on full choke but die when choke was turned slightly toward off, and backfire through exhaust. The spark was white and spark plug was wet with gas. Compression was/is good.

Cleaned the carb and adjusted the low speed jet to 1 and 1/2 turns; set valve lash to 8 thou (turned out to be close but not stock) and cleaned the magnets for the magneto which were well rusted. The magneto contacts were clean and the gap was/is 10 thou (spec is 15 thou). The spark was stronger but still white, but still no improvement in starting. So either change spark plug or magneto. The new magneto was in stock but $70 and not returnable so I put in a new NGK BR7ES spark plug (same as old one) and that solved the problem. Engine ran perfectly and started easily on first pull. 

In your case I would get a spark plug from a recognised manufacturer and clean any rust from the two flywheel magnets if you didn't do that with the new magneto. Just my thoughts.


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## MDchanic (Jan 17, 2020)

Motor City said:


> I would check compression, and if the cam skipped a tooth at this point.


Okay, these are two good questions. 

I never checked compression with a gauge because on any small engine I've ever worked on before, if I felt good compression on pulling the starter, I knew it was good. 
If I can pull the starter, and, if I don't pull it hard and fast enough, the compression will actually stop me cold, do I really need to use a gauge?

Do the cams skip on these?
I looked at the exploded view, and it looks like the drive gears are not located in any way that would allow them to skip or lose their synchronization, unless one stripped, in which case the valves wouldn't move at all. 
Is this something that actually happens?

Thanks,

- Eric


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## MDchanic (Jan 17, 2020)

Town said:


> In your case I would get a spark plug from a recognised manufacturer and clean any rust from the two flywheel magnets if you didn't do that with the new magneto. Just my thoughts.


As I said in the first post, I have tried three different spark plugs, the original Champion, which looked great, some brand I never heard of from "Lowwws," which was on sale for a buck, and a gold-colored fancy Briggs & Stratton super-deluxe one from the "Despot," and there was no change.

I have also tried three different Briggs & Stratton coils (with embossed logo and attached wire), the one that came on it, and two I bought on line from different dealers (in case one was bad). No change.

It's really burning my behind.

- Eric


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## Town (Jan 31, 2015)

But the original champion plug may have been faulty, so try a new one of good quality. Did you clean the flywheel magnets for the magneto?


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## MDchanic (Jan 17, 2020)

Town said:


> But the original champion plug may have been faulty, so try a new one of good quality. Did you clean the flywheel magnets for the magneto?


As I said, I tried three different spark plugs, the original, and two new ones.

I cleaned the flywheel edge with a sanding block until it was nice and smooth. Got a decent amount of dust off of it, too. 

I gapped the coils (all three of them) with the included card, which was in the 0.010-0.015" range.

- Eric


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## paulm12 (May 22, 2015)

is there an air leak on the intake somewhere, past the carb? I didn't read the you checked for that.


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## oneboltshort (Dec 16, 2019)

I would verify the valves and compression, that model cam has the steel shaft with plastic lobes and gear. They can and will spin around and drive you insane.


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## Shovel (Mar 26, 2019)

MDchanic said:


> Okay, these are two good questions.
> 
> I never checked compression with a gauge because on any small engine I've ever worked on before, if I felt good compression on pulling the starter, I knew it was good.
> If I can pull the starter, and, if I don't pull it hard and fast enough, the compression will actually stop me cold, do I really need to use a gauge?
> ...


You can check your can timing by doing the following.
With the valve cover off rotate the engine until you are in the overlap region of the cam... that will be close to TDC ..the exhaust will almost be closed and the intake will just be starting to open..the overlapping period occurs just before TDC and continues for a few degrees of rotation.



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## Motor City (Jan 6, 2014)

MDchanic said:


> Okay, these are two good questions.
> 
> I never checked compression with a gauge because on any small engine I've ever worked on before, if I felt good compression on pulling the starter, I knew it was good.
> If I can pull the starter, and, if I don't pull it hard and fast enough, the compression will actually stop me cold, do I really need to use a gauge?
> ...


I had a Tecumseh that had very low compression. You really had to coax it to start. Basically the compression was so low, it could barely suck the gas/ air mixture in to run.


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## MDchanic (Jan 17, 2020)

paulm12 said:


> is there an air leak on the intake somewhere, past the carb? I didn't read the you checked for that.


There is nothing but the carburetor, a 1" plastic spacer, and the head in the intake path, and there is no evidence of any of the parts not fitting tightly, but I can check by placing my palm over the carb and cranking it.

Thanks,

- Eric


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## MDchanic (Jan 17, 2020)

oneboltshort said:


> I would verify the valves and compression, that model cam has the steel shaft with plastic lobes and gear. They can and will spin around and drive you insane.


Okay, OneBolt, that photo shocked me, and it was exactly the sort of information I was looking for.

The exploded diagrams do not show that the cam is plastic. I would never, in a million years, have expected that.

Thank you very much for that. I will take your advice, and that of Shovel, and try to determine whether the cam has slipped in any way. I'll also do a quick search for whether there is a standard for degreeing the cam, which might give me a more certain idea than just assuring that the general valve movements occur at about the right time with respect to TDC. 

Thanks,

- Eric


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## Grunt (Nov 11, 2013)




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## Johnny G1 (Jan 28, 2020)

Why can I not see these utube's, not enough account post or what??????


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## Shovel (Mar 26, 2019)

Johnny G1 said:


> Why can I not see these utube's, not enough account post or what??????


Go to you tube and type in "Briggs plastic cam gear'



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## Johnny G1 (Jan 28, 2020)

Shovel, Thanks for the hint to watch these tubes, thought I could just click on them on the site but keep getting an error, Thanks again and I guess all these $100 motor's you see @ HF and princess auto are all built this way, Just hope my 270 Honda is not included in this kind of build.


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## Shovel (Mar 26, 2019)

Johnny G1 said:


> Shovel, Thanks for the hint to watch these tubes, thought I could just click on them on the site but keep getting an error, Thanks again and I guess all these $100 motor's you see @ HF and princess auto are all built this way, Just hope my 270 Honda is not included in this kind of build.


As a general rule the small Chinese engines are not bad
HF is built by the same MFG that supplies Toro 
MTD Powermore engines are built by Zongshen..which builds motorcycles and generators..The motorcycles have bullet proof engines..bit underpowered for displacement though as the heads are worked after casting.
As far as your Honda... as good as it gets..the Honda engines are what the others are cloning.



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## ST1100A (Feb 7, 2015)

One odd thing I have seen on some of those engines, not just Briggs, but Kohler and Kawasaki OHV motors, was a push-rod jump out of its socket on the rocker arm and then a valve would not open.
Many times we just depressed the valve a little bit to re-install the push-rod back in place and the engine ran again, but check the valve clearance first before starting the engine.
It appeared that the valve spring bounced and didn't have enough dampening effect, almost like a car with bad shock absorbers, and that was enough for the push-rod to jump out of its socket on the rocker arm.
Briggs and Kohler both had problems like that a few years ago on their V-Twin 25-27 H.P. engines. They had to re-design the push-rod end tips and the lifter cups, and the cups in the rocker arms, and they even made some push-rod guides to try to keep it from happening, they also played with changing the valve springs to give them a little bit more "Dampening Effect" to help combat the "Bounce" that was happening, they couldn't make the spring too stiff or they would have had other valve-train problems besides wearing out the cam lobes prematurely.
When it happens, it happens very quickly and in some cases it has led to bent push-rods or a hole in the valve cover, but not always.
If it happened on the intake valve, sometimes on the intake stroke the vacuum created was enough to draw a little bit of air fuel mixture into the cylinder to alter your compression readings and it could also make an engine "Fire-off" a little bit when trying to start it with starting fluid. The vacuum can actually open the valve a little bit, the springs are not very strong, especially when the engine uses a plastic cam.
It's an odd occurrence but it can happen, and it can happen even with the valve clearance set properly, but most likely when the adjuster backs way out causing too much clearance.


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## Shovel (Mar 26, 2019)

Shovel said:


> As a general rule the small Chinese engines are not bad
> HF is built by the same MFG that supplies Toro
> MTD Powermore engines are built by Zongshen..which builds motorcycles and generators..The motorcycles have bullet proof engines..bit underpowered for displacement though as the heads are worked after casting.
> As far as your Honda... as good as it gets..the Honda engines are what the others are cloning.
> ...


I meant to say the heads are not worked after casting.




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## ST1100A (Feb 7, 2015)

I also remember back in the early 2000's when John Deere had Kawasaki make their engines with the plastic camshafts for weight savings and all of the problems they had with them.
We replaced a lot of the cams with the new kit containing the metal cam, and even replaced a lot of engines because of the damage when the piston hit the valves.
A lot of those cams wore the lobes right off the cam and stripped off the gear teeth within a couple of engine operating hours.


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## MDchanic (Jan 17, 2020)

ST1100A said:


> ... a push-rod jump out of its socket on the rocker arm and then a valve would not open...


Nope. Checked that early on. Both pushrods in place and both straight. 

I'm home today and I think the wife may not have too many horse jobs for me, so I'll be measuring the valve lift and doing what I can to check the timing.

Thanks,

- Eric


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## MDchanic (Jan 17, 2020)

Okay, I went out and pulled the valve cover again (and all that stuff you've got to remove to get to it... ).

*First*, valve lift is the same on both intake and exhaust, at pretty much exactly 7/8". 
I believe that this should rule out having wiped a cam lobe.

*Second*, I actually measured the valve lash. It was a few thousandths tight on both valves, so I set them to 0.010" exhaust, 0.005" intake.

*Third,* I scoped out the valve timing. 
It looks as though TDC is actually somewhere around 1/4" after (counterclockwise from) the flywheel magnet. 
I assume that's correct, because the flywheel keyway is perfectly aligned with the crankshaft keyway (under the flywheel bolt), so the key did not shear.
The exhaust valve appears to _begin_ to open about 1/3 of the way from BDC to TDC, then finishes closing at the same point where the intake begins to open, about halfway from TDC to BDC.
The intake valve closes about 5-10° after TDC.

The timing seems about right to me for a low-RPM motor, but if anyone knows what the points are supposed to be, please let me know if this is right.

*Fourth*, After all of that, and without reinstalling any shrouds, I decided to try to start it again.
Now, instead of almost kind of halfway catching, it actually catches and runs at a very low speed ("Putt Putt Putt Putt Putt...") for anywhere from 5 to 30 seconds, then quits. It will only run with the choke closed, and adding any ether (choke open or closed) doesn't help. 

At this point I'm wondering whether the compression release on the camshaft is stuck.

Whadda you think?

- Eric


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## Shovel (Mar 26, 2019)

MDchanic said:


> Okay, I went out and pulled the valve cover again (and all that stuff you've got to remove to get to it... ).
> 
> *First*, valve lift is the same on both intake and exhaust, at pretty much exactly 7/8".
> I believe that this should rule out having wiped a cam lobe.
> ...


Your exhaust valve should be starting to open just before bottom dead center ..(little before)...it should remain open all the way for the upstroke of the piston and a little beyond TDC...just before TDC the intake will start opening..both valves will be 'cracked' open at TDC.
So in a nutshell if both valves are cracked open at TDC your cam timing is good enough to start.





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## MDchanic (Jan 17, 2020)

Shovel said:


> Your exhaust valve should be starting to open just before bottom dead center ..(little before)...it should remain open all the way for the upstroke of the piston and a little beyond TDC...just before TDC the intake will start opening..both valves will be 'cracked' open at TDC.
> So in a nutshell if both valves are cracked open at TDC your cam timing is good enough to start.


So, with my exhaust beginning around the middle of the upstroke from BDC to TDC and closing around the middle of the downstroke from TDC to BDC, it would seem like it's about 90° out of sync, which would seem to implicate the camshaft - perhaps the plastic gear turned on the steel shaft.

Does anyone know whether you can take the end plate off of a horizontal-shaft motor without removing the motor from the snowblower?

Does anyone know who came up with the idea for a plastic camshaft? I have a place I would like to stick this one.

Thanks,

- Eric


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## Shovel (Mar 26, 2019)

MDchanic said:


> So, with my exhaust beginning around the middle of the upstroke from BDC to TDC and closing around the middle of the downstroke from TDC to BDC, it would seem like it's about 90° out of sync, which would seem to implicate the camshaft - perhaps the plastic gear turned on the steel shaft.
> 
> Does anyone know whether you can take the end plate off of a horizontal-shaft motor without removing the motor from the snowblower?
> 
> ...


What you described sounds like the cam timing is off.
Easist way to tell is to catch the valves while both are rocking..exhaust almost closed... intake just starting to open...piston should be very close to TDC..you might be able to look with a flashlight down plug hole while jiggling flywheel back and forth a few degrees



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## MDchanic (Jan 17, 2020)

Yeah, reviewing my photos, the moment when exhaust closes and intake begins to open is definitely about 90 crank degrees after TDC, so that pretty much clinches it. 

So, 

Can I remove that crankcase end cover with the block still bolted to the machine? 

and

Do they make a steel cam, or am I just buying another piece of junk to replace the current piece of junk?

Thanks,

- Eric


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## Shovel (Mar 26, 2019)

MDchanic said:


> Yeah, reviewing my photos, the moment when exhaust closes and intake begins to open is definitely about 90 crank degrees after TDC, so that pretty much clinches it.
> 
> So,
> 
> ...


I expect you will have to split the engine..I am not finding any exploded views that I need that show a shortcut to get the cam.
I don't know if they have an all steel assembly available or not... I would look on eBay and Amazon...will find the part number(s) and post back shortly.



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## Shovel (Mar 26, 2019)

I found this... There is a metal gear available.
But when looking at the two separate cam numbers.. it gives no details nor a picture.

https://www.partstree.com/models/12.../camshaft-crankshaft-cylinder-piston-group-1/



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## Shovel (Mar 26, 2019)

You are in luck.
Jack's shows metal for that second cam number in my prior link.

https://www.jackssmallengines.com/jacks-parts-lookup/part/briggs-stratton/695285

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## MDchanic (Jan 17, 2020)

The cam seems to be #693404. I haven't seen any "all steel" units listed.
There's another, #695285, which, I believe, has an extended shaft for some sort of PTO, and which would not likely fit.

As far as I can tell, you just remove the bolts and tap off the end plate (which would be the sump bottom in a vertical shaft motor), then you can reach in and pull the cam out at TDC. My question is whether that plate can come off with the rest of the block still bolted to the machine. It's obviously easier if I can skip that step.

Thanks,

- Eric


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## MDchanic (Jan 17, 2020)

Posts crossed.

I believe that the all-steel unit is for machines with some sort of a cam PTO feature - its shaft continues out the back of the case for a couple of inches. I'd probably have to cut and machine it, which I am not well suited to do at this moment.

- Eric


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## Shovel (Mar 26, 2019)

MDchanic said:


> Posts crossed.
> 
> I believe that the all-steel unit is for machines with some sort of a cam PTO feature - its shaft continues out the back of the case for a couple of inches. I'd probably have to cut and machine it, which I am not well suited to do at this moment.
> 
> - Eric


Good eye I missed that...the metal cam is longer




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## 2.137269 (Nov 15, 2019)

better off pulling the motor off, with the horizontal engine reason is ,1 the cover is where you can't get it off in place and 2 as soon as you pull the cover and the cam the lifters are going to fall out of their bores, with it off you can better place the engine to work on it, kind of like upside down, with the head facing the work bench which will aid in the lifters staying put


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## Shovel (Mar 26, 2019)

I found this thread in another forum.
He had your part number and used a different one(cam)... Have to read further down for the actual cam.

http://www.diygokarts.com/vb/archive/index.php/t-23357.html

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## MDchanic (Jan 17, 2020)

So, the answer to the one question is: You've got to pull the block off of the machine, but the good news is, that's easy.

The engine has no control cables to it, and the gas tank is attached, so all you have to do is remove the belt cover (2 screws), remove the pulleys (1 screw, RH thread, backed it up with a pipe wrench on the pulley extension, easier with the block anchored to the machine than with it free), and remove four nuts holding the block to the machine (the bolts are splined in - no need for back-up). 

The bottom / end of the case comes off with six screws and a few taps, and the cam is right there. 

The answer to the big question of why isn't the motor running was right there: The plastic cam gear twisted on the steel shaft (it isn't even pinned on). Comparing stock photos of the new part with the part I have shows it clearly. The lobes stayed put. 

I didn't see the link above to the post about the Animal camshaft, so I went and ordered another stock plastic cam.
I don't expect any problems from here. 

Thank you all very much for your help, and especially OneBoltShort for letting me know that the cam was plastic and Shovel, for advising me on where the proper timing should be.

I'll let you know when it's running.

- Eric


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## Shovel (Mar 26, 2019)

MDchanic said:


> So, the answer to the one question is: You've got to pull the block off of the machine, but the good news is, that's easy.
> 
> The engine has no control cables to it, and the gas tank is attached, so all you have to do is remove the belt cover (2 screws), remove the pulleys (1 screw, RH thread, backed it up with a pipe wrench on the pulley extension, easier with the block anchored to the machine than with it free), and remove four nuts holding the block to the machine (the bolts are splined in - no need for back-up).
> 
> ...


Some of the videos I watched showed the plastic gear moving on the shaft..I expect that is what you will find as you stated.
Hopefully you will get more life from this one...has to be frustrating to have such a failure early on.





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## foggysail (Feb 21, 2015)

I don’t know if it was mentioned earlier, does the Woodruff key that secures the flywheel over the ignition points have any bend on it? It only takes a very,very small bend to misplace where the magnets are supposed to be for maximum spark.

This is a common reason why many lawn mowers fail to start even though the have fuel and spark.


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## MDchanic (Jan 17, 2020)

The keyways in the flywheel and the crank are perfectly centered when you remove the nut.

The cam gear is definitely rotated on the shaft, by at least 90°. Here are a couple of pictures:



















- Eric


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## oneboltshort (Dec 16, 2019)

Eric, It's been a while since I did one of these but I think the plastic one is discontinued and even when you order it, you get a steel one. I think I got a note in the box and may have said 693404 was now 693404a or similar.
Glad you got to the issue:wink2:


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## Fat City (Feb 11, 2017)

Have you checked the gas cap vent ? Take cap off, let vacuum escape, try again . Consumed fuel forms a vacuum as level drops. Gas Cap is vented to prevent this.


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## 2.137269 (Nov 15, 2019)

MDchanic 
thanks for the photo's and report . onebolt thanks for the part number supersede number info , 
never could understand why briggs had to play with plastic to start with, heck even the bigger singles had plastic pins holding the counter weights in place


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## Jesse11B (Jan 27, 2020)

Man, this has been a painful thread to read through. Mechanical failure of steel parts is one thing, but plastic parts in an engine is painful to see. Thanks for the detail in your postings. Good luck with it!


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## Shovel (Mar 26, 2019)

Jesse11B said:


> Man, this has been a painful thread to read through. Mechanical failure of steel parts is one thing, but plastic parts in an engine is painful to see. Thanks for the detail in your postings. Good luck with it!


I was shocked as well.. the engine had very little usage.
I don't think they all fail that fast.. he just had some terrible luck



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## Oliver Jake (Feb 6, 2020)

Its all about the Luck.


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## Sid (Jan 31, 2014)

Second time this winter, The dreaded Murphy's law.
Sid


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## MDchanic (Jan 17, 2020)

oneboltshort said:


> ... I think the plastic one is discontinued and even when you order it, you get a steel one.


OneBolt, Unfortunately, No.

Here's the new part:











The cam came in 1 day. Now I'm waiting for the paper gasket and the output shaft seal (Might As Well...), and I'll slap that bad boy back together. 

- Eric


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## MDchanic (Jan 17, 2020)

Here are a couple of side by side shots of he old and new cam, one with the gears lined up but the cams not lined up, one with the cams lined up.

You can see how far the gear twisted around on the shaft.



















- Eric


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## Shovel (Mar 26, 2019)

MDchanic said:


> Here are a couple of side by side shots of he old and new cam, one with the gears lined up but the cams not lined up, one with the cams lined up.
> 
> You can see how far the gear twisted around on the shaft.
> 
> ...


Thanks for the update...you found exactly what you thought you were going to find..the battle is almost over.



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## classiccat (Mar 1, 2014)

I replaced one of those in my briggs flathead quantum lawnmower engine.

You have to take comfort wherever you can find it...in this case knowing that the valves don't face the piston :grin:


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## Jesse11B (Jan 27, 2020)

classiccat said:


> I replaced one of those in my briggs flathead quantum lawnmower engine.
> 
> You have to take comfort wherever you can find it...in this case knowing that the valves don't face the piston


I sure agree with you there regarding the valves. I’ve have a Chevy Aveo(Daewoo) since 2006 as a gas sipper for long commutes. It has an interference engine that makes me nervous. 

I’ve done my timing belt changes a little on the early side to avoid losing the engine. Quite a few of the engines have blown due to the plastic timing belt idler pulley falling apart, and in turn the pistons and valves have a wrestling match


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## tabora (Mar 1, 2017)

Jesse11B said:


> Quite a few of the engines have blown due to the plastic timing belt idler pulley falling apart, and in turn the pistons and valves have a wrestling match


Or a boxing match? :wink2:


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## Jesse11B (Jan 27, 2020)

tabora said:


> Jesse11B said:
> 
> 
> > Quite a few of the engines have blown due to the plastic timing belt idler pulley falling apart, and in turn the pistons and valves have a wrestling match
> ...


Ha! Yeah that’s a better description!!


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## MDchanic (Jan 17, 2020)

Hey guys. I just realized I never posted my final results. I hate when threads are left without a resolution, and here I am doing exactly that. :icon-embarrassed:

So... I replaced the cam (two screws to hold plastic belt cover to body, one screw in output shaft to remove all pulleys [back up with pipe wrench on unused portion of pulley], four screws to hold motor to body [motor is surprisingly light to carry], six screws holding end cover on, tap with a bronze hammer to remove cover, four screws to remove valve cover, slip rockers off of pushrods to remove spring tension, pull out cam, check plastic timing gear on crank for triangular timing mark on one tooth [gear slides off crankshaft], reassemble with timing marks mating, lube moving parts with assembly lube, use new case cover gasket and use blue LocTite on output shaft screw), turned on the fuel, set the choke, pulled the cord, and it started right up and ran great. 

Now that it's working, where'd the snow go???

Thank you all again for your help! I learned something.

- Eric


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## 2.137269 (Nov 15, 2019)

MDchanic
thank you for posting the update and showing how easily they spin causing your issue

agree on the interference motors, valves loose pistons win


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## Gmax228 (12 mo ago)

Glad I came across this forum I was beating my head off the wall trying to figure out my low hours unit. This gave me the answer I was after now I just need to find the engineer that put a plastic cam in there and beat him to death with it. I wonder if they had a bad run of cams mine has almost the same MFG date as the OP.


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