compression issues, not sure why.

B

bigbutterbean

Active Member
I have a 66cc ht engine with a Puch 50cc high compression head and Arrow Cycles "Torquer" pipe. I pulled my head and checked my cylinder, and there are no scratches. The engine wont fire, and there is oil seeping from my head and my base gaskets. I have properly torqued my head bolts, yet I dont have compression. With the bike standing, I can push the engine with the clutch lever released, even though I know my clutch is properly adjusted. The engine does turn over when I try to start it, but does not fire. With the oil seeping from the base gasket - need a new gasket maybe? I purchased the engine new in April 2011. Anyone know if the base gasket should be replaced every so often, or have any other ideas? I'm at a loss.
 
Actually you don't need a cylinder base gasket. I use a gasoline resistant sealer. You just have to make sure you cover the gasket surface and that it's clean with no old gasket material still on it.

As for your compression loss that would be on the top end. The method for lapping the cylinder head has been posted here many times. I'm sure you've seen it. After you've dressed the head check the cylinder to make sure it is flat then install a new head gasket and torque the fasteners to the recommended 120 to 140 inch pounds. If this doesn't cure your problem start looking for a crack or bad spark plug threads in the head.
Let us know what you find.

Tom
 
bigbutterbean said:
Its a Puch head, its flat trust me. Its not the poorly milled cheapo chinese stock head.
Click to expand...
Have you actually checked it?
Lay a sheet of sandpaper on a piece of glass and run the head over it a few times. If there is any high or low spots you'll see it immediately. If you haven't checked it this way you don't know if it's flat or not. It doesn't make any difference who made it or where it was made, it must be flat on the gasket sealing surface. Same for the cylinder.

Tom
 
If the head wasn't properly torqued or came lose, you could of warped the head. Also read a post on the other forum where a the piston rings was broken, causing to loose compression.

Good Luck,

Chris
AKA: BigBlue
 
Last edited:
I worked something out with another member, so I'll be getting a replacement engine in a couple of weeks, hopefully that will hold me over till I can afford all the parts for my Schwinn/Lifan 49cc 4 stroke build.
 
if using acorn nuts on the head bolts, they may be bottoming which gives a false torque reading - throw some washers under the nuts, or get regular, open nuts
 
No, no acorn nuts, and I'm not fixing this engine, since I'm getting a replacement. The mods may close this thread or delete it if they wish, as I do not need any more help with this situation. Thank you for all the replies anyway.
 
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