# Craftsman snowblower bogging



## N3kf99 (Mar 2, 2019)

Hi all,
I have a Craftsman 536.886540. Its a 5HP 22 inch snowthrower that has been a beast all its life. Always started on the first or second pull for years. About a month ago, the wife left out a stainless water bowl for the feral cats and I hit it blowing snow. Yes the shear bolt sheared. I also had used that manufactured gas which was probably a mistake. I am using non ethanol now. Anyway, you need to use the electric starter to get it going. It won't start with the pull starter. Well not easily. Once running it propels fine and the auger goes on fine. But more then a couple inches of snow will cause it to stall. I figured it was the carburetor and replaced it. The new one does exactly the same, so not the carb. It runs fine without a snow load. So one of two things happen. The bowl getting stuck, screwed something up even though the shear bolt broke. Or the manufactured gas caused a valve issue. At least that's my guess. Any chance I might have slightly sheared a flywheel key? To me the always starting on one or two pulls and now needing a large number of pulls or the electric starter is a key also. Just not sure what I should chase down. Thanks.

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## N3kf99 (Mar 2, 2019)

N3kf99 said:


> Hi all,
> I have a Craftsman 536.886540. Its a 5HP 22 inch snowthrower that has been a beast all its life. Always started on the first or second pull for years. About a month ago, the wife left out a stainless water bowl for the feral cats and I hit it blowing snow. Yes the shear bolt sheared. I also had used that manufactured gas which was probably a mistake. I am using non ethanol now. Anyway, you need to use the electric starter to get it going. It won't start with the pull starter. Well not easily. Once running it propels fine and the auger goes on fine. But more then a couple inches of snow will cause it to stall. I figured it was the carburetor and replaced it. The new one does exactly the same, so not the carb. It runs fine without a snow load. So one of two things happen. The bowl getting stuck, screwed something up even though the shear bolt broke. Or the manufactured gas caused a valve issue. At least that's my guess. Any chance I might have slightly sheared a flywheel key? To me the always starting on one or two pulls and now needing a large number of pulls or the electric starter is a key also. Just not sure what I should chase down. Thanks.
> 
> Sent from my Nexus 7 using Tapatalk


Should mention it's a Tecumseh engine.

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## HCBPH (Mar 8, 2011)

You hit something with the blower and now it starts hard. You impacted the engine with a reverse stress, assuming it killed the engine at the time. First thing I'd do is check the key on the flywheel, chased one down once and that was the cause. Not likely the carb or magneto.


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## RedOctobyr (Mar 2, 2014)

Yup, slightly sheared flywheel key would be my guess too. I'd remove the flywheel and take a look.


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## N3kf99 (Mar 2, 2019)

Alright, I haven't gotten to the flywheel key yet. I put in a new governor spring and made sure the governor mechanism was clean and operating correctly. It appeared the governor screw was lose. Aha he went! Anyway, reset the governor. It now starts fine (even pull start) and runs and idles fine. Recovers from idle to full speed very well. However it still bogs down when snow gets into the auger. Even at a very slow forward speed. When this is happening, the governor has the carb wide open, but the engine speed stays low. If you stop forward motion, the engine recovers. And to repeat this is a new carb.

So I still need to check the flywheel key to make sure it didn't get crunched slightly. My question is this. Since I foolishly used the manufactured fuel (Tru fuel), is it possible that it ran hot and I got a burnt exhaust valve? Can a valve issue cause the engine to run ok under no load, but cause it to not run well under load? Assume the answer is yes, but never really dealt with a valve issue. Since I got to take covers off, I figure I might as well get a head gasket and take a look when I replace the flywheel key....

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## RedOctobyr (Mar 2, 2014)

A valve issue could cause varying issues, but I doubt that using Tru Fuel would be bad. This kind of application is exactly what that stuff is for. What said that using Tru Fuel is bad for the engine? That would be news to me. 

No need to take the head off, if you don't want to, at least when checking the flywheel key. You could do a compression check, and get some info that way. Or look closely around the head, to see if maybe there's a black area that looks like it's leaking combustion gasses. 

But a valve problem, or a head gasket leak, wouldn't really seem (to me) like things that would be caused by a sudden engine stop. 

With this said, have you checked your valve clearances? Valve clearance that's too tight can lead to a loss of power, as the valve doesn't close fully once the engine heats up. So you lose compression, and have leakage past the valve seat.


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## N3kf99 (Mar 2, 2019)

In order to get to the valve cover (the part where the valve springs and I assume you can measure clearances), it looks like I'll probably need to take off the carb and muffler. I figure if I go that far, I might as well pull the cylinder head off and get a look at the valves and piston. Does this engine have any compression relief for starting? If it does, how does one measure compression? It would seem the best you could do would be a leak down test. Of which I don't have equipment to do that. My cross reference says this is a Tecumseh HSSK50-67338N.

Anyway, I'll look at the flywheel key. Actually, I have a new one and I'll replace it. Then I'll know if it was damaged. If not, then it's time to look inside, unless there is an easy way to find if there is a compression leak. 

For the Tru fuel, you can find many stories about people having issues with lawn equipment after using it. Some talk about it runs hot and in some instances damages engines. Especially 2 cycles. I have a local has station that just started selling ethanol free, so I won't be using Tru fuel anymore. I think this thing is about 35 years old now. But old stuff is usually good stuff!!! Thanks again for pointers!!

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## N3kf99 (Mar 2, 2019)

So never believe the OP. Took the cylinder head off today, fully expecting to see an exhaust valve issue. But that seems to be closing tightly. I will check clearances. Lo and behold, you can see under the middle screw in the back, which goes through the flywheel/starter cover, there was a leak in the cylinder cover. Its small but you can see the carbon on the back of the cover. The screw was also quite loose. So that probably explains the lack of power. But it had nothing to do with the auger hit I had. I'll report back once it is fixed.

The question of the day. How the heck do you get the cylinder cover gasket off? It won't come off. It delaminated when I took it off, so its stuck to both sides.

I attached a picture of the valves and piston top. The cylinder wall looks fine. I assume this looks fine for a 35 year old engine. The carbon on the piston is very thin.









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## cranman (Jan 23, 2016)

Tru fuel should make the aircooled engine run cooler if anything...if this was me fixing, I'd pull the recoil shroud....pop the flywheel and check the key.....scrape the headgasket off with a sharpened putty knife.....torque the head back on...and try it out....


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## JLawrence08648 (Jan 15, 2017)

They do make gasket scrapers but I use a retired wood chisel, sharpened!


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## paulm12 (May 22, 2015)

When I take off the head, I go thru cleaning process first with a scraper and then something like this to fully clean and flatten/level the head: https://www.snowblowerforum.com/for...-diy-head-surfacing-after-gasket-failure.html

I'm also starting to use the synthetic wire wheels to clean up gasket material off of the head, the block and the sump covers. I use the softest one, I think is 4" dia, on a drill.


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## N3kf99 (Mar 2, 2019)

cranman said:


> Tru fuel should make the aircooled engine run cooler if anything...if this was me fixing, I'd pull the recoil shroud....pop the flywheel and check the key.....scrape the headgasket off with a sharpened putty knife.....torque the head back on...and try it out....


Yes I plan to look at key to be safe....


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## N3kf99 (Mar 2, 2019)

paulm12 said:


> When I take off the head, I go thru cleaning process first with a scraper and then something like this to fully clean and flatten/level the head: https://www.snowblowerforum.com/for...-diy-head-surfacing-after-gasket-failure.html
> 
> 
> 
> I'm also starting to use the synthetic wire wheels to clean up gasket material off of the head, the block and the sump covers. I use the softest one, I think is 4" dia, on a drill.


That is a great write up. Thanks!

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## RedOctobyr (Mar 2, 2014)

I've used a plastic putty knife as a scraper. You can also get brass putty knives. Using steel would make me a bit nervous about scratching the aluminum surface, but that's just me. If I was going to use a steel chisel, I'd probably sand down the corners of the chisel a bit (rounding them off, eliminating the sharp corners). To reduce the likelihood of a corner of the chisel gouging the aluminum head.


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## N3kf99 (Mar 2, 2019)

Well, got the valve cover off and the exhaust valve has no clearance. I am surprised this thing ran, yet alone moved any snow. Small cylinder head leak, and no clearance on the exhaust valve.

So the manual says the valve clearances should be .004 to .008. My intake valve is about a thousandth over .008, so .009. Other then above it seemed to run fine. Am I safe just leaving that or will I be sorry not be replacing the intake valve?

Thanks again. 

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## RedOctobyr (Mar 2, 2014)

I'd leave it alone. You won't lose compression. Just the tiniest bit of flow, and a little less decompression when starting.


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## HCBPH (Mar 8, 2011)

To dicarbon the head and piston, I use a combination of methods. First use brake cleaner and a plastic putty knife to remove the worst. I then use a true brass rotary brush in a drill along with brake cleaner to remove the rest even under the valve. It works out well for me.

Be sure if you do it that you get a real brass brush, not a brass coated steel bristle one. It won't scratch up the head or piston


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## N3kf99 (Mar 2, 2019)

It's alive!!! Thanks for all the help guys. After it was back together, and gas was put in, it started on the first easy pull. Let it run for about five minutes, turned it off for a couple minutes, and it started right up. Only way to start it up before was with the electric starter once it was hot. Sounds very smooth when it's running. Also a quick pull to start the auger previously could stall it. Doesn't even flinch now. No snow to try it in (unless I go to a store parking lot and get a couple buckets!). But I suspect it will run fine. 

Next fix for it, one of the screw holes for the electric starter is stripped. Not sure if I should tap it or just use a helicoil.

Thanks again!!!

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## N3kf99 (Mar 2, 2019)

N3kf99 said:


> It's alive!!! Thanks for all the help guys. After it was back together, and gas was put in, it started on the first easy pull. Let it run for about five minutes, turned it off for a couple minutes, and it started right up. Only way to start it up before was with the electric starter once it was hot. Sounds very smooth when it's running. Also a quick pull to start the auger previously could stall it. Doesn't even flinch now. No snow to try it in (unless I go to a store parking lot and get a couple buckets!). But I suspect it will run fine.
> 
> Next fix for it, one of the screw holes for the electric starter is stripped. Not sure if I should tap it or just use a helicoil.
> 
> ...


Well being an engineer, I picked up two 5 gallon buckets of very wet and heavy snow from a parking lot. Dumped a pile in the driveway and the snowblower went right through it without any issues. No sign of any bogging. Other then the wife thinking I'm nuts, I'm quite happy with the results!!!

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