loss of compression

[chazz]

ive lost compression in my engine,compression readings left to right of the motor are
no1 8
no2 8
n03 4
no4 8
i heve no head gasket leaks any ideas,im fed up just seems to be on going with this chop,might get myself a bandit or something

[jgordon]

ive lost compression in my engine,compression readings left to right of the motor are
no1 8
no2 8
n03 4
no4 8
i heve no head gasket leaks any ideas,im fed up just seems to be on going with this chop,might get myself a bandit or something

This doesn't sound right...You need to check the compression with the throttle wide open not that it will make a big difference with these readings. Did you have the cams out? Did you bend some valves? Give us a little history.

[argonsagas]

Those numbers can only happen if the compression gauge is broken or the cams are way off. That could happen if the timing chain slipped, putting the cams out of sequence, which could also lead to bent valves.


If the gauge is OK, then you will need to lift the valve cover and check the cams and remove the cover on the right side of the engine, by the footpeg to check the timing.

It is best to have a manual for this type of work, and follow it carefully.

[Billy Ricks]

This doesn't sound right...You need to check the compression with the throttle wide open not that it will make a big difference with these readings. Did you have the cams out? Did you bend some valves? Give us a little history.

If they are CV carbs open the throttle and manually get the slides up out of the way.

[DaveDanger]

The valves in that engine HAVE to bent or wide open due to jumped timing! I'd think you'd get at least 10 psi compression check with a hole in the piston large enough to drop a penny into. I'd very seriously look into the timing. I'm assuming that it won't even crank and run?? As previously requested... provide us a little history of recent activity/work on the bike/engine and we'll see what stirs up from the sludge on the bottom of our mental ooze pits .
I think we're probably all assuming that you are testing the compression by cranking the engine over for approximately 8 to 10 compression strokes per cylinder (Do them all identically) and with the throttle held wide open while cranking the engine over. If not... do so that way and post back with whatever results you have.

[chazz]

cheers for the help,ive just read what i'd written must of been hung over,the bike actually runs it just lacks power,it wont do over 70mph,so when a friend suggested checking the compression,so when i did the readings i got from the tester were,left to right
no1=115psi
no2=89psi
no3=60psi
no4=115psi
im just waiting on a top end gasket set before the strip down,i'll keep you posted cheers chazz