Need Help Low Compression! - Snowmobile Forum: Your #1 Snowmobile Forum

TCOLLINS · 11-19-2009, 08:23 PM

Left side 130 Right side 80

Just cleaned carbs and airbox. What can be done to fix compression? 1991 Yamaha Phazer II

orin250 · 11-19-2009, 10:38 PM

put a bit of motor oil in the cylinder with the low compression and then retest it it should bring it up close to the other cylinder if its a simple ring problem but if the oil doesn't make a difference then i would recommend taking the head off and investigating

TCOLLINS · 11-19-2009, 11:05 PM

Took head off and piston is trashed!

TCOLLINS · 11-19-2009, 11:06 PM

What would cause this and is it worth fixing?

nothingbutair · 11-19-2009, 11:23 PM

man im supperised that it is even holding any compression at all lolo. well it depends on what u think, hows the rest of the sled? do u got time or money? but i prolly would.

TCOLLINS · 11-19-2009, 11:29 PM

I'm thinking of tackling it myself. I have time it's just I don't know the cause of this. The sled is in very good shape. It has 6600 miles. It's a tough call.

nothingbutair · 11-20-2009, 12:16 AM

yeah i would prolly rebuild it, just check ure oil injection system. make shure that ure carbs are set correctually, then just take it easy forawhile then i would do a check over, then have at it.

**smallengineguy** · 11-20-2009, 06:13 AM

Does it have the stock exhaust on it? Usually when it burns the piston like that, somebody gutted the can. Either that or the port caught the piston.

DoubleClutch · 11-20-2009, 06:26 AM

Ive seen this before!! Thats a lean condishion! Check base gasket- crankseal- intake boot- carb pluged or set to lean. I seen the pic and wondered how you got photos of the yamaha SRV I rebuilt a couple mounths ago. Snuck in the shop snapped a couple pic's and left and didn't even bring any beer! See how you are!! LOL

BIGTRUCKBALLIN4 · 11-20-2009, 07:44 AM

Theres youre problem,no sorry, man piston pin travel(side to side)who knows really,fix it,enjoy winter.Segs,got it port could have caught the piston top.The top of the piston doesn't look like it went lean.

TCOLLINS · 11-20-2009, 09:52 AM

Quote:

Originally Posted by smallengineguy

Does it have the stock exhaust on it? Usually when it burns the piston like that, somebody gutted the can. Either that or the port caught the piston.

Seg I think you're right. The ring is definately warped which may have caused the ring to get caught up on the exhaust port chipping off the piston.. The port and cylinder looks fine. I will continue to dismantle to inspect further. Yes the exhaust is stock and untouched.

TCOLLINS · 11-20-2009, 09:55 AM

Quote:

Originally Posted by nothingbutair

yeah i would prolly rebuild it, just check ure oil injection system. make shure that ure carbs are set correctually, then just take it easy forawhile then i would do a check over, then have at it.

The walls are coated with a nice layer of oil so I think the injection system is working properly. I just cleaned the carbs which were very dirty and blocked. May have led to this problem?

clodev · 11-20-2009, 11:18 AM

I had this happen on my wifes 85 ss440. i just replaced the piston and rings on it. Mine was due to the cooling fan seperating from the metal shaft so it wasn't getting enough air on the clutch side. Only broke it in this summer so not sure i didn't have any air leaks in the engine or bearings so we will see.