what were your ring end gaps prior to installation?
what was your piston/cyl wall clearances?
these are CRUCIAL for building a reliable / high HP engine....
compression 'can' be bled off via various issues.... valve seating is ONE of them..... so make sure your valves are seated properly and not cupped/damaged.... then there is valve TIMING... make sure your timing chain has not jumped or the possibility of the cam gear FLANGE rotating on the cam itself.... (it happens, just not often).... then the obvious decompressor issue, which you seem familiar with and have already dealt with.... and yes, at .040" gap you should have over 150psi and easily to the point where she would be too stiff to even kick over....
confirming everything MECHANICAL is OK with your lower end? crank and/or rod journal bearings ?? when you last rebuilt it and this issue occurred....what EXACTLY did you replace? piston? rings? cylinder? you mentioned... how about CRANK???? just curious..... you say this has been an on-going issue...so we need to know what occurred when it FIRST showed up.... I assume since your last rebuild she has NEVER had the proper compression???
if so....and your valve train is OK.....your probably correct in assuming the piston and/or cylinder were out of spec..... the ring gaps and piston/cyl clearances will give us this information.....
let us know.....g[/b]
I don't remeber the exact number of the ring gap, but I did check it and it was in spec with what my service manual said.
I do not know what my piston to cylinder clearance was, I did not even check it. I just figured that since both the cylinder and piston were new, OEM parts they would have to be within spec.
As far as valves, I think they should be in great shape. They still have the same shims from when the bike was on the showroom floor. And all of them are still in spec...
I did check the crank for any excessive play when I was inside the motor, and it feels and looks great.
This problem started last year. I tore the motor down to replace the cylinder, piston, rings, pin, and head and base gasket. There was nothing ''wrong'' with any of the parts, I just wanted to make sure that I would have the motor in top shape for the season.
Now before I did this rebuild, she was running GREAT. Starting was easy, always on the first or second kick.
So I installed the new OEM cylinder, new OEM piston/rings/pin (and I checked ring gap) and new OEM gaskets. Finished putting the motor back together and tried to start it... She fired up after about 15 kicks. This is when I first noticed that the kicker was easier to kick. Ran it for a few days like this thinking that maybe the rings needed to seat. Well it never got any better, ran kinda weak and was a pain in the ass to start.
When I just recently I took the motor back apart, I was thinking that maybe I damaged the head gasket or piston rings somehow when I installed them. So I installed new rings, new base gasket and a new head gasket. I reused the same piston and cylinder. This made the problem no better. This is when I adjusted the decompressor to .040'' clearance and still can only get about 85 PSI when kicking it as hard as I can, with throttle wide open.
I bought a Harbor Freight Leak Down Tester. For some reason, I can't get it to give me a reading of how much air leaks out of the combustion chamber. The gauges don't move...... But I CAN'T hear any leaks coming from the exhaust or the intake.... however I CAN hear quite a bit of air coming from the crankcase.....and it makes a gurgling sound too.... I know rings don't seal 100%, but should it be easily noticable with only 15 PSI of air being pumped into the cylinder?