1996 VMAX mystery issue

 

I have a1996 VMAX with 42000KM on it. never had any trouble with it.
Yamaha serviced at 30000KM (valve adjust/carb sync) . Stored in
winters. started up fine this summer,BUT..I was freeway driving at
70MPH when sudenly "lost" a cylinder and had minimal oil coming out LF
(#2) cylinder and was running very rich. Have 200PSI compression in LF
cylinder,all rest 150. leakdown test was 11%. Found nothing to cause
such a loss..

left the bike to sit for 3 days,started up and it ran
acceptably,perhaps a little "rich". any suggestions of what cd have
happened to  cause that little "fart" that went away all by itself??
thanks

 



what is your storage drill?

 



The difference in compression should not exceed 10% . Several things jump to
mind as to possible cause(s) of your problem. most immediate is some sort of
head gasket problem, after that check the valve/lifter assembly perhaps one
exhaust valve is not opening all the way (which would explain both rich
condition and higher compression) I've seen lifter/rocker assembly slip of
center before also bent fulcrum assembly. I believe that the v-max has
removable cam covers. you  may be able to visually inspect the movement of
the valve train on the affected cylinder. hope this helps

 


I was going to say that possibly an oil ring got stuck - pulled in oil (talk
about rich!) then left some in the cylinder causing a fake higher CR
resulting in the 200psi reading.  Leave it for a bit (or drive it), the ring
gets unstuck, life goes on as normal.

Try the compression test again (assuming all is normal) and see if it's more
of a level playing field now....

 

that makes sense..stuck oil ring...i will drive for a bit (which i
have done) and then re-check compression.

thanks.




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