viperboy101
New member
Hey guys. Was wonder what the compression should be on a viper. I got 122 on the pto side ? And 14O on the other two. Thanks
super1c
Super Moderator
All depends on gauge. Dont focus on number focus on difference in numbers. I do a check cold and warm. Cold i get 115, 123, 123 on both my vipers. Pto always lower. I gain on those numbers when warm. So i would say your pretty close. Make sure you give it a good 10 pulls with throttle open.
Snowsnake
New member
PTO is lower right from the factory on these motors for smoother idle/balance supposedly.
I heard the PTO is lower because of lack of cooling on the cylinder 
s10mike
Member
given that the pto is supposed to be lower, i think those #s sound real good
viperboy101
New member
Okay thanks guys. Was worrying a bit. Forgot to mention that the sled has 22000 km on it. Should I maybe do the rings or something ?
hlmrx1
Member
- Joined
- Jan 6, 2005
- Messages
- 31
You could do a leak down test to see if the rings are ok. I had heard that the cylinder on the PTO side had lower compression so that the main jets could be the same on all three cylinders. Other triples that have the same compression compensate for the heat with a different size jet. I can't see how lower compression on one cylinder would make the moter smoother, if anything it would tend to make it rougher I would think.
in the off season you should do them. as the # look ok, finish the season before you touch it unless it really has you worried.
ottawaair
New member
Yea, lower compression for the hot cylinder, then run straight jetting. Stupidest idea ever. The jets are much easier to change than the compression. I would get an aftermarket head, all 3 will be the same comp. then. Then stagger your jetting like on a srx.