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Craftsman snow blower not running well.

20K views 29 replies 8 participants last post by  scipper77 
#1 ·
I have a 2005 8.5 HP Craftsman model 536.881851 (Briggs)

This season I noticed a surge at idle. Now after a half dozen uses it is really hard to start. I have never used the electric start before, now it's the only way I can start it. After starting it seems to run pretty good but in my opinion it bogs down "a little" easier than it should.

I have checked compression and several turns of the engine with the electric start brings the reading to 75 lb's. From what I understand this number doesn't mean much because there is a pressure relief mechanism for ease of starting.

In the interest of full disclosure I think the original owner replaced the shear pins with regular bolts. I have bogged the engine pretty good on occasion so I'm at piece with the possibility of needing a major repair.

There is a spot on the heat shield (front side of motor) that looks like someone has held a torch to it (discolored).

Now that I have the lengthy description out of the way I'll tell you what I'm thinking and then hopefully someone here will ignore my opinion and tell me what I need to do to determine the issue.

From the idle surge I thought the carb was the issue. Now with the very sudden change in starting performance and the hot spot on the front heat shield I'm thinking there is a leak in the head gasket. That leak would cause a lack of compression making it hard to start. Carb may also be an issue.

What do you guys think??

(Mods, I think this thread may be more appropriate for the small engine forum. Please move it if you think I'll get more help over there)
 
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#3 ·
I agree that you have a carb problem. I would first try some SeaFoam and see if that makes it better. If not, then a carb disassembly & cleaning is needed.
And make sure you buy the correct shear pins for it. $8.00 for shear pins versus $50 for an auger gear and more if the gear breaks the housing plus the down time and aggrevation of repairing it.
 
#4 ·
Make sure the carb-to-engine bolts/screws are tight. Check for gasket leaks in that area, too. I agree that it's running lean, and you probably have to disassemble the carb and give it a thorough cleaning. But, start with the easy stuff.
I'd like to add stress to installing the proper shear pins - that could save you from a mechanical disaster.
The hot spot could well be caused by running lean, and the extra heat is not doing your engine and the exhaust valve any good.
 
#18 ·
After thinking about this post I went back out and pulled the main jet from the carb. It looked clean to me but I poked some wire through it any way. After reassembly I could get the motor to start by hand for the first time in a long time. It didn't start right up like it used to however. After running it on some area's of the driveway that I usually don't bother with (driveway is 4 cars wide at the top) I shut it down and could not quite get it to restart. It would sputter a little like it was going to start but it wouldn't start.

I have a feeling that whether the head gasket is bad or not you hit it right on the head with your first post about running lean and heating up the valve.

Thank you for the good advice even if it took a little time for it to sink in.
 
#5 ·
I hope you guys are right.

Before I posted here I had added a fuel cleaner to the gas and cleared the driveway.

Yesterday I used it. I primed it set the choke and pull started it (it would not start.)
then I plugged it in and pressed the starter button. It backfired, I could see a flame come out of the carb, but did start without too much trouble.

I think I will pull the main jet and see if I can clean that. With it "running" I really don't want to pull the whole carb off to clean until the season is over.

My biggest concern is that I may cause severe damage if I run it when I know there is something wrong.

At the end of running yesterday the unit was holding a steady idle.

Also, is it possible to reuse the gasket for the main jet or do I need to get a new gasket before I even begin?? It's so easy to pull the main jet that a trip the store is 10 times more effort than checking the jet.
 
#8 ·
I'm convinced it's a head gasket or something like this. Today I tried to start it but forgot to turn the toggle switch to on. When I remembered and turned the switch it started but smoke came out from behind the heat shield. Attached are some pics as I know we all love pics.

I have trouble believing this is from the carb...




I'm likely going to tear into it this summer if it's not that complicated.

Can someone tell me how hard it is to replace a head gasket on a small engine like this?

Please any comments on my problem are appreciated even if they are things like your screwed... At least that bumps this thread so others might see it.
 
#9 ·
Head gaskets are not difficult to change. Flathead engines are very easy, overhead valve engines are still pretty easy. You will get plenty of help and encouragement here, so no big problem even if you haven't done one.
 
#11 ·
I can only start it with the electric start. I just don't know what else it could be and sure don't want to burn out the head.

I'll keep my eye out for a replacement with a bad motor just in case I need parts. I'm sure buying parts from sears will get pretty pricey.
 
#14 ·
What is involved in removing the head on my OHV motor?

Do I have to take off the rockers or will the head come right off leaving the push rods behind?

A new head is $77. If the head is damaged is it likely that the block is also?

These questions are to help me decide if I should tear it down now or park it and work on it in the spring when the weather is a little bit more friendly.
 
#15 ·
Basically, pull the sheet metal cover(s) off, remove the rocker cover, remove the pushrods, remove carb and exhaust connections, remove head bolts, remove head.


My 2¢ - running it may do (more) damage. You have to weigh that against the need to use the machine and the time it would take you to repair it. A head gasket isn't very expensive, it's mostly the time to replace it. Plenty of others on here have done it, so they can help. I have never had to do it (yet) on a small OHV engine, although I have done quite a few on flatheads.


Does the new head come with valves, etc? That's a factor in pricing and work.

Repair manuals can be bought, and would be a help.
 
#16 ·
Finally, I get to lend some assistance!

Firstly, I had carburetor issues as well. As I will describe in a post of my own, I found great success with replacing the carb all together. I'm not the most mechanically inclined guy, but I found it quite manageable.

Secondly, I successfully replaced a head gasket on a Kohler engine from a '77 Wheelhorse. Again, for a not-so-mechanically-inclined person, it was quite easy...both to find the right part and to replace it. I had someone with a torque wrench help out with the bolts for proper torque.

I hope this helps, or is at least encouraging.
 
#17 ·
This morning I removed all the covers etc I could. I could not figure out exactly what all needs to come off to remove the heat shield that is burnt in the pictures. Here is what I found in my limited tear down....

The exhaust valve was white like a spark plug would be that was running lean. I'm not sure if this is normal since it is after the combustion chamber.

The gasket for the exhaust pipe had a burnt area. No big deal to me since it's after the head and really easy (and cheap) to replace.

The burnt area on the heat shield is right where the head meets the block next to the exhaust valve.

The head bolt near the leak was not very tight. I wouldn't say it was loose but it was pretty easy to snug it down a little bit more.

After I tightened the head bolt and put everything back together I still couldn't start it by hand but it started pretty easily with the starter. A definite improvement from before.

My conclusion is that the heating and cooling of the motor caused that stud to loosen over time which in turn caused the head gasket to fail. Tightening the head bolt made the leak smaller but the head gasket is still bad.

At this point I feel pretty good about tearing into the motor but I am not sure exactly what all needs to come off in order to get that heat shield off, and the head of course.

Any words of advice or encouragement would be greatly appreciated.
 
#19 ·
You're quite welcome!

I would change the head gasket regardless. If it was loose, it's probably damaged. It's not a huge project, and it may be worth the $ to get a repair manual for that engine. You might even find one on line here. It should give the torque values for the head bolts, and the tightening sequence.
You should be able to eyeball the engine and see how the cover comes off, but there again, a manual could be helpful.

An exhaust valve can have white deposits on it, that's normal. The intake valve is usually darker because it gets cooled by the incoming fuel mixture.
The hot spot on the shield just might be exhaust gasses leaking past the head gasket instead of going out the exhaust pipe.

Keep at it, you'll get it running right soon enough! And, you'll learn some good stuff along the way.
 
#20 ·
Yup, I am with you on everything you just said. The head gasket is definitely going to get replaced. Before the problems began on this unit it would start on the first pull when the motor was cold. It always took more effort to start after it had been warmed up. If it goes back to a one pull start when cold I'm not going to touch it this season. I'm pretty sure that there is a HG leak however so I'll be tearing into it again at some point.

I'm actually pretty excited to do this job. I'm a little concerned with getting the valves adjusted correctly when I put everything back together but I'll cross that bridge when I come to it.
 
#22 ·
So winter ended and I put the snow blower away. Now that summer is waning I decided it was time to tear into the snow blower.

Long story short I was lazy to not address this issue in the winter and it looks like I got away with it. The problem is a bad head gasket. $10 or so and I should be back in business.


The head and block are not scored, just a little carbon deposited.


I plan on cleaning things up a little and reassembling. All other gaskets look like new and will be reused except the one for the exhaust pipe.

Can I just use a scotch brite pad to prep the surfaces for the new gasket or is that too abrasive?
 
#23 ·
you can't really see it to well from the picks but it seems to me that there may be a casting defect in the area where the gasket blew out. Since the original lasted a couple of years worth of use I guess I will just have to hope for the best and if I need to I will replace the gasket every couple of years. I contacted Briggs to see if they wanted to compensate me for the casting defect (ie send me the $5 gasket for free) but I'm not expecting much there.

It has been recommended to me to spray the new gasket with copper gasket sealant. That's what I'll do.
 
#24 ·
Time to put this thread to rest.

Briggs customer service was really top notch on this. I emailed them a pic and asked for a new head gasket. They replied asking for a better pic of the casting defect. I cleaned up the block and found that there is no casting defect or damage to the block or head. I emailed briggs back and told them that there was no defect and all I wanted to be happy was the torque spec and sequence for the head bolts.

After that email I bought the head gasket from Sears parts direct. Two days later briggs emailed me back with the relevant pages from there manuals to reinstall the head. Oh and they told me that they sent me a new head gasket even though I told them that there was no defect on there part.

The blower is now back together and starts on the first pull again. And I have a spare head gasket too.

I found an old Aliens blower on the curb yesterday (1973) and tore into it to find the connecting rod in pieces. I am stoked to fix this one now, but that's another thread.
 
#25 ·
I found an old Aliens blower on the curb yesterday (1973) and tore into it to find the connecting rod in pieces. I am stoked to fix this one now, but that's another thread.
If your plan is to fix the old engine make darn sure the rod didn't knock a whole in the block as it probably did. If it has electric start remove the started and check that. If your plan is to swap the engines with something else then good luck :)
 
#28 ·
I'm guessing from your avatar that you have done a similar repower (that ugly blue HF motor really stands out lol).

Do you know if I can use the 20% off coupon on a motor? The small print only says no generators.

Back to the issue with the first blower.....

The exhaust stinks. I think it might be running lean but maybe I am just paranoid. Is there anything I can do to adjust the air fuel mix?? At this point I'm not too worried as I have a potential second unit and a spare head gasket if the same issue repeats. But I am finding that tinkering with small engines is becoming addictive.


I might just start cruising Craigslist for equipment with bad motors just for something to do in my spare time.
 
#29 ·
I am not familiar with the newer Briggs. My guess is the carb isn't adjustable, but you could look on the bottom of the carb for a screw. When I bought mine I used a 20% off coupon, but I think most of the stores stopped taking them for engines. Doesn't hurt to try though.
 
#30 ·
OK, so this thread got a little off topic when I found a second blower project. Now that the second project is complete I would like to return to the original blower.

When the engine runs with no load and the choke off it hunts ever so slightly and i think it sounds like it is sneezing a little. It is very slight but when I apply a little choke the motor smooths right out and runs like a clock.

I am not sure if the engine is just bouncing off of the governor, or if there is a lean condition that the choke corrects.

A really have no idea how to address this or if it even needs to be addressed. I'd hate to rebuild the carb out of paranoia.

Any advise on this would be awesome.
 
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