low compression both cylinders(60 psi)

[jeepguy]

so i was testing compression today and got almost exactly 60 psi in both cylinders.

things to keep in mind:
Engine has never run with me.
Rephased
new pistons and rings
cam chain adjusted correctly

What should be my next step, or things to look for. It seems weird that both cylinders are the same but so far off??

 

[tonyc]

Check your guages to see if that is a true reading.

 

[pa23driver]

if you recently replaced the rings and pistons then you have to wait for the rings to seat properly before you can get an accurate compression reading. also, and this is important on these bikes, when checking the compression make sure you hold the throttle wide open while you are kicking it over.

 

[azman857]

Was the carbs held open? Valves lapped in and adjusted?

 

[jeepguy]

Carbs where off did not lap valves about the ky thing I didn't do not sure why though dooh

 

[TwoJugs]

Crank speed plays a big role too. Since they are both 60 might be a cam timing issue too?

 

[jeepguy]

so possibly just need to re-check my timing chain adjustment?

 

[5twins]

You might try to get it to fire up and then do another check after it's warm. You get better readings on a warm engine.

I've been into the top ends of several of these. All needed the valves lapped. All had some that leaked. Just like replacing the cam chain and front cam chain guide, I feel this is something you just do when in there. You have to replace the valve guide seals anyway (or you should) so the valves will be disassembled. Might as well lap them.

 

[HooliganCycles]

Like mentioned above, with new piston and rings you will not get an accurate reading untill the motor runs and the rings are seated, untill then it will read low, i just built a motor, when it was all done compression was 75psi, put about a thousand miles on it now compression is 170

 

[jeepguy]

ok well i am in the process of trying to get it fired up, and it wasnt, so thats what led me to test compression just to see what it was. i suppose i will pop the top off and do a little valve job.

 

[Triggerton III]

I have exactly the same problem after a top end rebuild. it did run for a while although roughly.