Very low compression, what to look for?

Lassociety · Post by **Lassociety** » Wed Jun 25, 2014 3:24 am

This is a perfect situation for a leakdown test. Find Top dead center of compression and find a way to lock the crank. (put bike in top gear and roll it, then lock wheel or hold brake sometimes works in a pinch) Pressurize the cylinder with compressed air through the spark plug hole. (use the same adapter that you used for the compression test) pressurize the cylinder and listen carefully for air coming through the exhaust, If so you have a bad exhaust valve or seat because there should be NO leakage here. If you hear air coming through the carburator, You have a bad intake valve or seat, there should be NO leakage here. You will hear air coming through the crankcase breather since air WILL get by the rings. At least you can narrow it down or eliminate the valves this way.

deafanddiabetic · Post by **deafanddiabetic** » Wed Jun 25, 2014 11:16 am

Damn, now I wish I would've performed the leakdown. I suppose I could put it all back together and give it a try? I got wild and took it apart last night, the pistons are still in their cylinders but I can definitly see some scoring on the left hand cylinder (the one that didn't work). The valves I'm in the process of taking out but the actual camshaft is tough to remove, I'm not sure if it's reverse threaded or not.

Here's just a few pictures, it might not be indicative of anything yet without reaaally looking at them, but is this helpful? I can't tell any differences in the valves yet besides being really black and mucky. What's a good solvent to clean up these things? I see some burned deposits around the lip of the exhaust ports, I think it'll clean up though, I don't think the actual metal is scored or burned.

deafanddiabetic · Post by **deafanddiabetic** » Wed Jun 25, 2014 11:21 am

Apologies for the giant pictures. So, the scored piston cylinder doesn't feel very deep grooves, I can't feel them at all actually, but I presume that's a bad thing. The more burnt looking valves are from the "good" side.

LOUD MOUSE · Post by **LOUD MOUSE** » Wed Jun 25, 2014 5:14 pm

I suspect Stuck Rings. ..........lm

deafanddiabetic wrote:Apologies for the giant pictures. So, the scored piston cylinder doesn't feel very deep grooves, I can't feel them at all actually, but I presume that's a bad thing. The more burnt looking valves are from the "good" side.

deafanddiabetic · Post by **deafanddiabetic** » Wed Jun 25, 2014 5:20 pm

Mouse, I just ordered some standard sized rings (52mm, I believe). I plan on just putting them on regardless, but is there anything to help unseize those? Putting some oil down in there, or is it better to just replace them?

Thanks for the input.

LOUD MOUSE · Post by **LOUD MOUSE** » Wed Jun 25, 2014 5:25 pm

I'd say if you have new rings install them after you ball hone the cylinder. ............lm

deafanddiabetic wrote:Mouse, I just ordered some standard sized rings (52mm, I believe). I plan on just putting them on regardless, but is there anything to help unseize those? Putting some oil down in there, or is it better to just replace them?

Thanks for the input.

deafanddiabetic · Post by **deafanddiabetic** » Fri Jul 04, 2014 6:56 pm

Well, I'm officially unemployed as of today and I thought I'd tackle my engine to celebrate. Immediately I found that my valve puller tool, piston ring compressor tool and piston rings are all the wrong size so it looks like I won't be doing ANYTHING this weekend...

But besides that disappointment, I've read through the manuals but can't seem to find out what size piston ring I need to order. These I got into the grooves but they won't push down into them, they're all cleaned out and ready, but I think the top two are way too thick to fit. I also broke the oil ring because I can't for the life of me figure out how to get it all the way down to the last groove?