1998 GTX 951 LOW COMPRESSION REAR CYLINDER

[ronaldjamesh]

I purchased this 98 GTX from a friend 3 years ago.
Had carbs rebuilt and fuel lines replaced at that time.
Currently has 232 hours in it.
Stored in heated shop all winter.
This summer installed new battery and when I started it for the first time on trailer, it did Not sound right.
I Immediately shut it down and started trouble shooting. Only ran for 5-10 seconds.
Replaced plugs, cleaned Rave Valves.
Same result. Proceeded to check compression and found 125 on front and 75 rear.
This Ski ran fine when I parked it for the Winter.
I was Super busy last fall/winter and neglected to Fog the engine before storing.
Have since removed exhaust manifolds, rave valves and carbs.
I do not see anything scored or unusual.
Reeds are all there and seem to operate normally.
Used bore scope to look at top of piston and see no damage.
Oil pump is pumping oil into intakes of both cylinders.
Next step is to pull engine and tear down.
Hate to do that if I don't have to.
Any ideas or suggestions would be much appreciated!
I have two other 951 carb skis, a 2000 with 530 hours and 2001 with 275 hours. Both still run Great!
This one has me stumped! Thanks!

 

[mikidymac]

I would pull the head and look before pulling the engine. But yes, with those compression numbers so far off you have an issue in the low cylinder.

 

[Ckrawiec]

Have you considered a little oil/Marvels Mystery/Tranny fluid down the spark holes and working the PTO manually to get things lubricated before you tear it apart......you didn't fog the cylinders last hibernation so things will be dry....just a though before surgery.