No Compression

pup55

pup55

New member
Joined
Mar 21, 2007
Messages
285
Age
64
Location
Boylston Ma.
I have a 1996 v-max 600 with a bad piston. I replaced both pistons and rings.The sled ran good for a day then it started to run poorly. It was hard to start and did not have any power. I did a compression test on both cylinders and came up with 100 on left side and 30 on the right. The right side was the side with the good piston but now it is the one with the low compression. Could anyone tell me what might have happened? When i replaced the pistons with new ones it still took about 10 to 15 pulls to get it started. My 95 v-max 500 starts on the first pull. Need help? Also the pistons came with a hole on one side. Could someone tell me what that hole is for and what side does it face? Thanks
 

Was anything wrong with the cyl's,what caused the motor to fail in the
first place?,,more info..

was it getting enough oil?????
 
Yes I showed it to a yamaha dealer and he said it was caused by snow being sucked into the air intake. That is what caused the piston to fail the first time. Only the bottom half of the piston was damaged. I could start the sled and run it.I had the cylinder cleaned up and put it back togther with 2 new pistons. When I put the new rings on the right side they were tight. I called yamaha and thet told me to hit the rings with light sand paper to take off any burrs. Could that have been the problem? Also do you now which way the hole on the piston goes and what the compression should be.
 
On a '96 you should have all of 130ish,can't remember if '96's still had the
thin head gasket like the '95's did, what you mean rings were on the tight
side? did you need to file the ring end gap some?? yes that's a problem
if the ring end gaps are too tight,they need room to expand.

there should be a arrow(->) stamped on the piston that goes to the
exhaust side,hole to the intake side
 
Check the tapper of the juggs. I had a problem like yours and it would run but when it warmed up it would cut out and be hard to start after it. You should have at least 125lbs of compression in good running condition according to one of the guys at Snowest. If you have 100lbs or less I would consider taking the juggs off and taking them to a machine shop to be mic -ed.
 
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