COMPRESSION...help

C

Collin_750sx

i just tested the compression on my 93 kawi 750sx. the rear cylinder read 135psi and the front read 155psi. is this bad that they are different?

im going to mill my head to run about 175psi, how much material should i get taken off
 
Matt_E

Matt_E

steals hub caps from cars
Site Supporter
Location
at peace
A 20psi difference is indicative of a problem.
I would double and triplecheck those readings.
If they are valid, you should at the very least remove the head and determine what the cause is.

Do all this before you even think about milling that head.
 
C

Collin_750sx

i checked it multiple times and then i pulled the head off. everything looks ok with everything? im thinking i just need a top end rebuild? after that im going to be milling the head. but i dont know how much material to take off. is there anything else that can be causing the compression difference. the gasket looks good, but there was some moisture between the head and the gasket
 
jeepmark4x4

jeepmark4x4

Backflip, weeee
Location
Marietta, GA.
If you got some water down in the crank, or if the crank area is foaming up...might cause some bit of difference in compression. Take the head to a shop and make sure its not warped. You can find aftermarket heads for 750's rrreal cheap, just look around. But it definitely sounds like at least a top end. Good luck!
 
Matt_E

Matt_E

steals hub caps from cars
Site Supporter
Location
at peace
Collin_750sx said:
i checked it multiple times and then i pulled the head off. everything looks ok with everything? im thinking i just need a top end rebuild? after that im going to be milling the head. but i dont know how much material to take off. is there anything else that can be causing the compression difference. the gasket looks good, but there was some moisture between the head and the gasket
Click to expand...

With the head off, measure how far below/above the deck each piston is at top dead center.
On the low compression side, the rod may be bent.
 
jeepmark4x4

jeepmark4x4

Backflip, weeee
Location
Marietta, GA.
I'm sure thats what it is....top ends on ski's just go out, it sounds like it went withOUT a bang which is good. The best of the worst case scenario is that the top end just wares out and loses compression, no detonation or overheating.
 
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