Compression?

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Oct 27, 2003
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#1
Ive just rebuilt my top and bottom end of my first dirt bike-a 1985 yz125. What is the specified compression for this bike? Im getting about 120 psi but I think this is low.
 

Studboy

Thinks he can ride
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Dec 2, 2001
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#3
Did you check the ring end gap? Are you testing with the throttle full open?
 
Joined
Oct 27, 2003
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#4
Whats the ring end gap? And no, im not testing with the throttle open. Should I? And also Im testing at cold conditions not operating conditions.
 

jboomer

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Jan 5, 2002
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#5
Sounds like you're doing it ALL wrong. You should be testing it on a warm engine, with the throttle wideopen, and keep kicking until the gauge quits rising (5 or 10 kicks).