# Pull flywheel or not to pull flywheel on Briggs 8hp



## Twes (Feb 13, 2016)

Good afternoon all, 
I've been reading the past posts in regards to sheared flywheel pins and the likelihood that is the issue with a no start condition. Wondering if I could get your opinions on what my next move should be. A bit of history ........28" Craftsman with Briggs and Stratton Powerbuilt snow 8HP. My brother in law was using it without issue last storm when he ran out of gas (is what he said) he refilled the gas and could not get it started immediately after. He stated it was fresh gas and he had previously filled up with the same can earlier that day without issue. I picked up the machine from him and first thing I discovered was a shop rag in the impeller . I didn't appear to be bound up and I removed it pretty easily. He stated it came to a "normal stop" when it ran out of gas . At this point I was suspecting the rag perhaps momentarily caused stress and sheared the flywheel pin upsetting the timing but figure I would rule out the regular/potential issues...................
.Removed float bowl and everything looked/smelled good. Machine was just running ok so didn't expect anything but figured I'd check. 
Drained /cleaned tank to rule out possibility of water in the fuel. 
Verified there was spark with an in line spark tester. There is in fact bright spark when motor is cranked. 
Does anyone know if I would still get spark if the pin is sheared? Not sure if I could still get spark but not have ignition due to incorrect timing.......unsure what my next best option might be. Thanks everyone!


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## RIT333 (Feb 6, 2014)

If your snowblower is belt driven, which I am almost positive it is, then it is almost impossible to sheer the flywheel key by hitting an object. Even if the sheer pins do not work, it is most likely that the belt to the pulleys on the crank will slip before sheering or bending the flywheel key. Lawnmowers - yes, but I have never heard of a snowblower with that problem.

Anyone else hear of this ?


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## Twes (Feb 13, 2016)

Makes sense now that you say it, the belt would slip/break before the pin would shear......unlike a mower where the blade is directly connected. At a loss as to why it would all of a sudden not start. Especially since I get spark with the tester.......


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## RIT333 (Feb 6, 2014)

If you get spark, are you sure you're getting fuel ? Try either starting ether, or a splash of gasoline. Maybe the flywheel key got sheered a little and the timing is off a little. Just seems odd though. I guess it is worth a look.


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## JLawrence08648 (Jan 15, 2017)

Spray starting fluid in the carb, if it starts you have fuel or carb problem.

You don't need to pull the flywheel to see if the key is sheared. Remove the pull cord housing, you will see it from there. It does not have to move slot, only a little then it needs to be replaced.

A strong spark is not an indication the key is not sheared. A spark means the coil and such are working and it's not grounded somewhere.

The key is for the ignition timing of the engine, that the spark at the spark plug is going to spark at the right time when the piston is at the top if 0 TDC or near whatever the manufacturer has designed for, and both valves are closed.


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## RedOctobyr (Mar 2, 2014)

Another vote for trying ether or a little gas sprayed into the throttle body, to see if it will fire if you supply fuel a different way. I assume it still feels normal when you pull-start it, and as we know, engines need fuel, spark, and compression to run. You *should* have fuel, it sounds like you have compression, and you at least have spark at some point, now you may need to confirm that it's at the proper time. 

I would also expect the belt to slip before shearing the flywheel key. But last year a coworker's lawn tractor started giving him trouble. After some investigating, he found that the flywheel key was sheared. Tractors, like blowers, are belt-driven between the engine and the transmission or blades, there's no direct connection like on a walk-behind mower. So it surprised me, but it can happen. Of course, if the flywheel nut wasn't tightened enough, or the tapered surface had oil on it, it would become easier to shear the flywheel key. 

Good tip about just removing the starter cover to check the flywheel alignment, though!


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## Twes (Feb 13, 2016)

Thanks for the responses ,
I tried spraying some starting fluid into the carb while starting and it didn't help. Doesn't try to start at all. The pull cord doesn't feel any different than before (not easier, either, or jerking ) I didn't realize it was possible to view the sheer pen without removing the flywheel. I had previously removed the pull start shroud but only could see the plastic flywheel and the metal "cup" on top of it (not sure what it's actually called)


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## Motor City (Jan 6, 2014)

Even taking the nut off the flywheel and inspecting it, doesn't ensure it isn't sheared. I had it happen to me on a tiller.


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## evh (Jun 22, 2015)

Ok, this likely is not the issue, but I will share. You used the term "bright" spark. I had a small riding lawn mower with an 8hp Briggs that ran fine and then would not start. I checked for spark and it had a "bright" spark. I use that term because the issue was the spark plug had gone bad. My experience is the spark should be just a small blue arc between the gap. This broken plug was more like a flash on a camera. I changed the spark plug and all was good. Again, I am keying on your terminology of the work "bright. Good luck.


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## JLawrence08648 (Jan 15, 2017)

The keyway is under the cup. If your machine is on the new side, the flywheel will come off easy, pull it, wiggle it, or give it a tap. Nothing else will fall apart. Sand the magnet on the flywheel so it's shiny.


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## Twes (Feb 13, 2016)

It's not so new , I think about 10 years old but I will give it a shot. Also should mention I tried pulling the plug cleaning it up and it looked good, also sprayed a bit of starting fluid in before putting it back , not even a sputter ....


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## RedOctobyr (Mar 2, 2014)

evh said:


> Ok, this likely is not the issue, but I will share. You used the term "bright" spark.
> ...
> Again, I am keying on your terminology of the work "bright. Good luck.


When I was chasing an ignition problem one time (not on a blower), I tried deliberately closing the gap on the spark plug until it was close to touching. I wanted to make it easier for a spark to jump, when under compression, in case the ignition system was weak. For a test, I wasn't worried about losing some power due to a spark that was too small, I just wanted to see if I could get even a "pop" out of the engine. After the (failed) test, I re-gapped the plug properly. 

And I agree, replacing it is cheap insurance. I had an old blower that was hard to start. The plug's spark looked OK to me, but it started a lot more easily once I replaced the plug.


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## Kiss4aFrog (Nov 3, 2013)

I'd pull the flywheel and inspect the key to see if it's bent and that there isn't any damage to the keyway in the crank or flywheel. I agree that the belt should take the shock but that is still a "should". If the belts in good condition and tight there still might be enough force from that flywheel trying to spin against that crankshaft to do some damage. Especially on an older machine that may have been jammed a few times in the past.

https://www.google.com/url?sa=t&rct...RRIAT--Nn5SzU077Q&sig2=jE97kChJ-Gdf7neNwxyX6Q


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## Twes (Feb 13, 2016)

All sounds good, Gonna replace the plug (cheap insurance/troubleshooting) and take a peek at the flywheel alignment .......then check back...thanks!


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## Grunt (Nov 11, 2013)

I would say that if the engine is mechanically sound, it should sputter or backfire even with a sheared key. Is this an overhead valve engine? If it is, one of the push rods may have bent or slipped out from the rocker arm.


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## Twes (Feb 13, 2016)

I believe it is ohv. Hopefully that's not the case but will def keep in mind if replacing the plug and inspecting the flywheel alignment doesn't turn anything up.


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## jtclays (Sep 24, 2010)

I agree with Grunt, pop the valve cover and inspect. Briggs OHV have possibly the weakest valve springs in small engines in my experience. They frequently bend push rods or the rockers will pop out of position. When you take off the valve cover, do it slowly and look for valve stem caps if you see one of the rockers out of place. Kinda tilt from top to bottom when you remove. Lot easier to check this than the flywheel key, so hopefully that's it.


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## JLawrence08648 (Jan 15, 2017)

Grunt said:


> I would say that if the engine is mechanically sound, it should sputter or backfire even with a sheared key. Is this an overhead valve engine? If it is, one of the push rods may have bent or slipped out from the rocker arm.


Good point. I'm surprised no one else mentioned this. We are so use to working on heads.


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## JLawrence08648 (Jan 15, 2017)

It may be the carburetor. I had a ohv lawnmower that ran out of gas and I could never get it started, not even with ether. Swapped carburetors with similar mower and it started right up. The "bad" carb would not start on that machine, put it on another mower, same, would not start. And I had disassembled it, soaked it in Gerrymandering ChemDip, ultrasonic cleaner, never started on 3 mowers.


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## RedOctobyr (Mar 2, 2014)

Twes said:


> The pull cord doesn't feel any different than before (not easier, either, or jerking )


Checking the valves certainly isn't a bad idea. 

But because the pull-starting it doesn't feel different, I'm guessing that the valves are likely functioning normally. If a spring had come off (or a pushrod bent, etc), and a valve was staying open, you'd lose a lot of compression (which is why the engine wouldn't start). But I'd expect you'd also feel the difference, in that case.


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## Grunt (Nov 11, 2013)

RedOctobyr said:


> If a spring had come off (or a pushrod bent, etc), and a valve was staying open, you'd lose a lot of compression.


If a push rod bent or came loose from the rocker, the valve would stay closed and a possible increase in compression would be felt because the ACR would no longer work.

ACR = Automatic compression release.


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## RedOctobyr (Mar 2, 2014)

My apologies, you're right. I was thinking about it wrong, thanks. 

So, for instance, if one valve never opened, the engine would be unable to breathe properly. Whichever valve was staying closed, it would not be able to bring in a fresh charge of air & fuel, and then discharge it for the next cycle. Either it can't inhale, or it can't exhale, but in either case, it's going to be a problem (it needs to do both to bring in fresh air). 

Removing the valve cover and watching the rocker arms is an easy way to check the function of the valves. 

Thinking out loud, one other way that you might be able to help check this would be to remove the spark plug, and add a very small amount of fuel through the hole. Reinstall the plug, attach the wire, pull the cord, and see if you get a single "pop" from the engine. 

But this is a very "indirect" sort of test, only useful if you're uncomfortable removing the valve cover. Removing the cover is a much better method for checking the valves.


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## Twes (Feb 13, 2016)

*Resolution finally!!*

First off thanks very much for all your replies and input to the thread! I learned a ton throughout the process of getting the blower running again. The culprit ended up being the valve (intake) was WAY out of adjustment. So much so that when I pulled the valve cover off the tappet (not sure if thats what its called) was off the valve stem and inside the valve cover. Didn't appear that anything was damaged, readjusted the Valves and its fired right up perfectly. not sure why/how that would happen so suddenly but its purring now so pretty certain that was the issue. Thanks again for sharing your wealth of knowledge!!


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## RedOctobyr (Mar 2, 2014)

That's awesome, congratulations! I'm glad you got it figured out. And thank you for posting an update and sharing your findings. 

Did you have to change the rocker arm adjustment much, from how it was? Did you pull the pushrod out to check it? If the pushrod got bent somehow, that might allow it to pop out from under the rocker arm. And if you simply adjusted the rocker arm to work properly with the (bent) pushrod, that might simply delay having another problem. 

I hope it was simply a fluke, and nothing more. But if something got bent in the process, it could cause an issue again in the future.


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## Twes (Feb 13, 2016)

Hmm I didn't remove the pushrod but looking back probably should have. I may take a few moments and do that before I return it to my brother-in-law. The rocker arm adjustment seemed to back itself out so it needed quite a bit of tightening. (Almost as if the locking nut didn't do it's job). I will report back if I find anything bent or out of the ordinary.


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## amuller (Jan 3, 2016)

I don't know much about the OHV Briggs, but the older ones usually used an aluminum or zinc key, the idea being that the key could shear without damaging the crank or flywheel. These don't usually shear if properly installed, but if someone has had the flywheel off for ignition service and not torqued it properly, or had the taper surfaces clean and dry, it might be sheared. On the ones with the flywheel nut built into the starter clutch it is hard to torque correctly without the special tool. (https://www.jackssmallengines.com/j...ratton/19244?gclid=cpfjzufyp9icfqw4waodvh4j8q). With most Briggs ignition systems without points, if the key is sheared you can still get a normal spark but it won't be timed right so the engine will likely not run.

So, if you have tried the usual things you may need to get into the flywheel. Briggs manuals are on line.

Alan


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## Grunt (Nov 11, 2013)

Twes said:


> readjusted the Valves and its fired right up perfectly.


Glad to hear that was your problem and all is well. :goodjob:


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## RoyM (Feb 7, 2017)

Did you properly torque the rocker stud? Sounds like it may have backed out. It is not often a problem on snow engines, they don't get hot enough, but has happened. It is common on lawn tractors when the cooling fins get plugged with grass.


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## 524SWE (Jan 20, 2017)

Twes said:


> Hmm I didn't remove the pushrod but looking back probably should have. I may take a few moments and do that before I return it to my brother-in-law. The rocker arm adjustment seemed to back itself out so it needed quite a bit of tightening. (Almost as if the locking nut didn't do it's job). I will report back if I find anything bent or out of the ordinary.



This is being seen more often as these engines get older. Frequently these engines require valve adjustment after the first 25 hours and every 100 hours after that. Tightening the jam nuts to hold the adjustment is frequently done without a torque wrench and the recommended 70-110 inch pounds or roughly 6-9 foot pounds is either overtightened or under tightened leading to what you found or worse, the stud broken off.
I can't emphasize enough how important it is to consult your manufacturers engine manual for the proper torque settings. It could have been worse.


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## Twes (Feb 13, 2016)

I did not torque down unfortunately. Prob gonna pull the cover again to inspect the rod and will torque down at that time.


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## StressSolutions (Dec 11, 2020)

RedOctobyr said:


> Of course, if the flywheel nut wasn't tightened enough, or the tapered surface had oil on it, it would become easier to shear the flywheel key.


Thanks for this, it's probably my issue.


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## 140278 (Aug 27, 2020)

welcome to the sbf

please watch last post dates if old start a new thread


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## Kiss4aFrog (Nov 3, 2013)

StressSolutions said:


> Thanks for this, it's probably my issue.


Welcome to SBF StressSolutions









Feel free to start a new thread if you're still having problems.


.


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