Honda S90 Low Compression (70PSI)

alle0615

New Member
I have new piston, rings, gaskets, new valves and newly cut valve seats and an OK cylinder. This is a complete top and bottom rebuild (by me) and I am curious if some minimal pitting and scoring on the cylinder would cause such low compression alone or should I be chasing something else down? Thanks! Picture is bike in question just for fun. I had it running and had some shift drum issues so decided to rebuild, compression was 100 ish previously.
IMG_1776.JPG
 

Tripod

Well-Known Member
Dratv offers cylinder boring and or cleanup services. Ive used them twice for this and am pleasedw with the results and how easy their process is.
 

Old Guy Too Many Bikes

Well-Known Member
You're seating new piston rings, and it may take time to break in. Try adding just a bit of oil in the cylinder. I'd fire it up, let it run a bit, and check compression again. I've never seen a S90 with a twin rear sprocket. I hope that rear tire's going away.
 

alle0615

New Member
Thanks, I did and it is up to 100 now. The rear wheel came with it but yeah I haven't either and yes the tire is toast and going once the other 10 problems are sorted out. Any idea why the motor only runs with kick starter pushed all the way down? If I let the kick starter go back to normal position the engine dies...
 
Top