C River Yamaha
New member
I did a comp check on a 02 viper today that i was lookin at buyin it ran great but when the motor was cold i did the comp check and i got 140 psi on the mag side 140 psi in the middle and 118 psi on the pto side is this normal with the vipers or is that cylinder goin to the way side... Thanks
goody_700
New member
Seems to be a pretty big margin to me... How many times did you check it? Did you try it again after the first time? What kind of quality is the comp tester? You may get a different reading if you didn't pull the cord the same, screw in the tester tight, etc... The engine MAY be fine, it MAY NOT be, just be SURE, don't buy something unless you KNOW.
Hope this helps.
Hope this helps.
That's only 15 o/o of the others...not all that much...a leak down test is a better way to judge...if in doubt, pull the exhaust off & W manifold & take a look...
tedgoesfast
New member
i was also taught that 10 to 15 percent only inbetween all double check gauge if ok ispect exhaust side of that cyl
JeepTherapy
New member
Isn't that about correct with the staggered compression of the Viper?
Mtnviper said:
yamyrider
Active member
that would be about correct with the lower compression out of that cylinder for a Viper.
journeyman
Active member
The middle and the mag sound very good. The PTO side sounds a bit low. Our two Vipers run very strong. We have around 127-130psi on the PTO side,while the other two are about 136-139psi. This is taken on a cold motor, ignition off and throttle cable pulled open.
daman
New member
for future reference a comp test should be done @ op temp with throttleC River Yamaha said:
open,,,not saying that's your problem here, just saying...
C River Yamaha
New member
Ok thanks guy's i'll look into it farther and try some different things...Thanks for all your help....