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Discussion Starter #1
What would cause a motor to have low compression, 60 psi? I changed the rings with no change. Would a head gasket do this or would a head gasket give zero compression?

LD[:(]
 

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What did the valves look like when you had it open? If it has a burnt valve, then it will leak up and won't have good compression. (both intake and exhaust) OR, if they just don't seal well, then you will have lower compression. Now I don't know much about exactly what kind of engine a Honda ATC 110 has in it (hopefully we aren't talking about a 2 stroke, because they don't have valves like a 4 stroke) but thats just my experience......
 

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If it's on a Honda ATC like you mentioned, than it could be a number of things: blown head gasket, cracked head, leaky valves due to carbon build-up or just badly seated due to wear or even mal-adjusted or a broken valve spring. That motor should have at least 150 psi. Is the head properly torqued?

that's my best guess.
 

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I would say the valves,thats a common thing on those when the get some use on them..maybe not though
 

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i just went thru and cleaned out my vavles on my 82 atc 200 yep it was low compression due to valves being dirty and needing adjustment
 
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Many of those Honda engines are built the same way from 50cc to 110cc.

It would be my guess that the valves are not adjusted properly. They have solid lifters and if not adjusted with the correct clearance the valve will stay open and cause leaking. If I remember right the intake will be set at about .008 thousands and the exaust will be at .010. If you don't know the specs. these numbers will be in the ballpark. Set it to these numbers and then recheck the compression. Remember you need to have the piston TDC on the ingition cycle so both valves are closed when setting the gap on the tappet. Do this with a cold engine.

Dennis
 
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I just thought of something else. If you just changed the rings you had to pull the head off. When you did this you had to take the timing chain off. You must install the timing chain with the marks all lined correctly. It has been along time sence I had one of these apart but there is a mark on the gear and a mark on the chain. Look on the flywheel. There should be a mark that lines up with something like a notch or a scale of some type. Set the flywheel so the marks line up and look at the timing gears and chains to make sure everything is lined up like it needs to be.

If you are one tooth off, on the gear, the valve will be opening to soon or to late and causing low compression.

Dennis
 

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Discussion Starter #8
D Noel, thanks for all of the input. I did not line up the marks. Would this cause that much reduction in the compression? If it was the head gasket, then I would have 0 compression, right? I think that it could be the valves, I didn't bother to clean them although they did look like they had some carbon buildup. Would dirty valves cause that much reduction in compression?

Thanks to everyone.

LD
 
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It has been almost 30 years ago that I had one of those apart but I think the timing chain has a gold colored link and the gear has a round dot or a punch mark. These must be lined up. I bet you may have turned the flywheel a little bit when you were working on it, then it would have changed the valve timing. Yes, you would have low compression if the valve timing is off. For example, the piston would be coming up on compression and the intake would still be open. By the time it closed the piston would be to far up to the head to make the full 120psi compression. You would get a low number, consistantly.

If you have a nice dealer, he may copy the pages you need from the overhaul manual. A good book or reference is worth a lot of mistakes.

I did my first rebuild on a Honda 50. I was in the third grade. My next rebuild was on a Honda 70 in the sixth grade. I haven't opened one up sence. Moved to outboards, two stokes and snowmobiles.

Dennis
 

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Discussion Starter #10
Oh, one more thing that I should add is that it constitantley backfires from the exhaust pipe, could this prove that the timing is off? Thanks for all of the feedback. I think I'm close to fixing this problem,

LD[:I]
 
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Yes it would backfire. The flywheel also controls the ignition timing. If you moved the flywheel from Zero position and installed the head without the valve timing being in the correct position it could be making enough compression to fire and then the exhaust valve opens and "pop" out goes the fire through the pipe. From your description, I would bet money that you got things back together without the valve timing being in sink with the crank timing. The Zero mark on the flywheel will be TDC "Top Dead Center"

Both the valves should be fully closed and the piston at the top of the stroke.

Let us know when you get it figured out.
 

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Discussion Starter #12
Well, I modified the timing and it definately was off. I still have very low compression about 60 psi and the backfire condition is gone. How can I tell if my valves are leaking?? Is there some easy test to do?? What else could it be, I just changed the piston rings???[V]
 
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Did you set the valve tappet clearance? On the top and the bottom of the head there is a round cap that covers the tappets. You can take these off with a large cresent wrench. The tappets will have a small jam nut and a square headed threaded adjuster. You need to set the clearance between the valve stem and the adjuster so that there is at least .008 clearance. on the intake and .010 on the exhaust. I don't know the compression specs for that engine, it most likely is not a real high compression engine if I remember right. Have you got it to start yet?

Dennis
 
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