compression problem

[Kidd700V]

My sx 700 on the pto side has 40 lbs of compression on fresh rebuild the cylender had been re plated and the rings are seated it pops and misses until about 3000 rpm then cleans right out and everything is burning with a laser temp gun all cylenders are at about 500 degrees at the exhaust port at 3000 but hot or cold compression is at 40 lbs i was wondering if it could be a stuck reed as my reeds dont seem to seal very well any info would be appreciated thanx matt

 

[skidooboy]

what are the rest of the cylinders reading? if they are all within a few pounds, i say your comp tester is bad. sxr/srx/viper will pop and sputter when given throttle before warm up, especially if a plug is fouled or starting to foul. with new motor, assembly lube/fogging oil can foul plugs in short order. ski

 

[Kidd700V]

the other two cylenders are at 125 lbs it is just that pto side cylender that is low

 

[skidooboy]

better pull it down and measure the piston wall clearance, piston, and cylinder dimensions and look for something wrong with the cylinder. even though it was redone, doesnt mean it was done correctly. ski

 

[greg]

Check the head gasket for leaks around that cylinder.

 

[Kidd700V]

thanx for the input guys any other info would be great

 

[daman]

I agree,,i would be tearing into it..

 

[yamaholic22]

are you sure the rings aren't upside down? I've seen that before, will definately do the same thing.

 

[yamyrider]

how can you tell when a ring is upside down

 

[daman]

There's little dots on them,,they go up