Haven't updated in a long time. My bike is almost finished but i have low compression on the front cylinder. around 120-125 when the engine is at working temperature, compared to ~140 on the rear. i think this difference is contributing to the fact that i cant get it idle properly ,it wont stay a 1200 rpm, but it will hold 1800-2000 rpm. valves are adjusted, pickups good, ignition timing good, carbs are overhauled adjusted and balanced. i have an oil leak that seems to be from the base of the front cylinder, can this have an affect on compression (it's pretty bad and get worse when the engine is running). also, what are the chances that only the piston rings are bad? i'd hate to take the motor out now after the entire bike is built, changing the rings on the front cylinder seems to be fairly easy with the engine in place. but not on the rear. will it be an awful sin to try that first? since the cylinders are nikasil coated, will they probably be ok? according to the odometer the bike did 88000 km (but of course i cant know that for sure) what are my options? Thanks
Hope someone can provide a guidance that I certainly cannot. Share some updated images the bike was/is lovely'
Cylinders should be within 10% so you are just about there. at 125/140 with engine cold check front and rear compression on the starter ignition off, then add a small amount of oil to the front cylinder and check again, if the compression coms up its probably rings, if it makes no difference its probably a valve not seating but its not enough difference to worry about unless the cylinder drop below 110psi IMHO at that milage
Put some oil in the cylinder, (through the sparkplughole) not very much. I did this on my Mille when I had low compression on the front cylinder. This happens when the bike has sat for a long time. The compression was increased when i put oil in the cylinder.
