Low Compression RXT-X 260

[kissthecoder]

About the ski
- Purchased a 2014 RXTX with low compression but all cylinders are pretty even
- Dry: 104,98,95 Wet: 110,110,114
- The ski has 32 hours and looks brand new inside and out, especially the inside
- Starts up easily but is sluggish compared to my other one (which I used to verify the compression gauge works)
- Hits close to 65 and about 7600 rpm but takes a while to get there
- I'm unsure how it has such low and even compression with low hours except that it's originally from a northern state and could have sat during winter and rusted the rings.

Questions
- I plan on doing a leak down test, but wondering if there's any other tips or things I should look for while doing so.
- Any possibility the timing slipped?
- If the leak down test indicates the rings, would you consider a rebuild worth doing?
- It looks like a rebuild costs a lot more than I was hoping.

 

[ski-d00]

This is why the compression test doesn't mean much and BRP doesn't even recommend doing them because the results can be confusing at best. I've seen SC motors at 110 on all 3 and ran perfectly for many years at full speed and acceleration. Do the leakdown test and go from there.

Not likely the cam/crank timing slipped but can be checked pretty easily. It electronically is constantly adjusting fuel/spark timing to make it run perfectly at all rpms.

 

[kissthecoder]

This is why the compression test doesn't mean much and BRP doesn't even recommend doing them because the results can be confusing at best. I've seen SC motors at 110 on all 3 and ran perfectly for many years at full speed and acceleration. Do the leakdown test and go from there.

Not likely the cam/crank timing slipped but can be checked pretty easily. It electronically is constantly adjusting fuel/spark timing to make it run perfectly at all rpms.

Couldn't find a way to hold the crank shaft in position during the leak down test and will come back to to that later.
I did find something: the timing disc melted and was wedged in the chain:
- The melted piece didn't move at all while the engine turned over.
- TOPS looks like it is damaged from whatever happened
- Pulled out what's in the picture.
- I bet theres more somewhere else but don't see any pieces
- How bad of an idea would it be to keep riding.

 

[ski-d00]

Very bad idea. There's a metal disc that snaps into that plastic part that is floating around in your pto housing that could end up in your chain which will destroy the engine. I would pull the motor and remove the pto housing and fix it correctly.

 

[kissthecoder]

Very bad idea. There's a metal disc that snaps into that plastic part that is floating around in your pto housing that could end up in your chain which will destroy the engine. I would pull the motor and remove the pto housing and fix it correctly.

Thanks for the advice! Finally got around to getting the motor out.
- Used crank locking tool, timing was off by 2 teeth on the cam gear. Fixed that
- Found thrust washer at the bottom, like you said it was. (Undamaged)
- Also found some the plastic pieces and they seem to have made their way in the passage that leads to the crank
- Figured splitting the case will be worth doing since motor is already out
- One of the crank case cover bolts is really stuck and the impact tore right through it.
Questions:
- Is it concerning to have oil between the crankcase stretch bolts and cover bolts?
- Would applying heat and a bolt extractor be a good approach to get it out?

 

[ski-d00]

Is it concerning to have oil between the crankcase stretch bolts and cover bolts?

No, that area is part of the oil sump and the design. The o-ring is what seals the oil.

Would applying heat and a bolt extractor be a good approach to get it out?

You can try a little bit of heat but the scotch grip is pretty far down so typically doesn't work well. I've had some that had to grind a slotted groove near the edge along with a flat spot so I could lay a screwdriver flat and then hit a with hammer to get it to rotate.