2008 Ski Doo Summit Low Compression

[Sekeith]

Took the Sled out to the lake over the long weekend and had the engine shut down on me while racing across the lake. It was the end of the day and thankfully it fired right back up after maybe 30 seconds and I was able to get it into the trailer under its own power. Started her up today and it sounds like there was a miss fire or something as the sled was shaking more than normal and wouldn't go into reverse. Smelled like it was running a bit rich so I started by pulling the plugs.

The details:
2008 Ski Doo Summit Everest 154" apprx. 1050 miles (bought it last year with 911 mi on it)
- Pulled the plugs (BR9ECS) and one has the beautiful copper look of a good running cylinder, the other black from carbon (both will get replaced)
- Compression test (cold engine, WOT) shows clutch side has 135 PSI and the other 95 PSI

My thoughts are I probably cooked the rings when I was tearing across the lake at the end of the day (should have bought ice scratchers) and need to at the very least replace the piston rings on the one side to get the compression same in both cylinders. Checked my oil container and she's definitely using oil at a good rate so no worries there.

Can I just do the piston rings in one cylinder or is it better to do both since I'll have it opened up anyway? Any thoughts if there might be something else causing the low compression on one side? I don't have a leak down tester so I'm kind of at the limit of my current testing abilities. I'll tear the carb apart at the same time and make sure she is nice and clean for future rides, not sure if there is anything else I should check for/lube up/maintain before firing it up again.

Thanks in advance

 

[neilsleder]

For the price do both pistons and rings in both cylinders! I suggest rk drop in kit. Had that in my 09 and worked really good! Good idea to check the crank now to.


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[Giver800]

x2 on doing piston and rings in both cylinders and checking the crank while its opened up. Also may want to look into doing dual ring pistons its not essential but is recommended by most.

 

[Sekeith]

Thanks for the input, I'm going to start by splitting the cylinders and taking a look at what I've got in there. May need to have the cylinder hones for replaced if there is major scoring and might as well do it right the first time.

 

[tex78]

No honing a Nicaseal cylinder

If it's that bad, needs repaired and re Nicasealed

 

[Sekeith]

Ah, that's good to know. So I started pulling the sled apart and found this melted hose. Anyone have any idea if it is supposed to plug into something or where the heck it goes? Was planning on pulling and cleaning the carbs but they look like a g.d. nightmare to get out.

 

[Sekeith]

No one knows? I think it is supposed to go to a tee that connects both rave valves, not sure tho cuz mine doesn't have a tee they are just connected together. But I pulled off the rave valves and poked the pistons and rings a bit. Everyone keeps telling me I can tell if they need to be changed from there but they both look the same to me so I'm just going to go ahead and keep pulling the cylinders off. If I can get the last two bolts off the y-pipe. Any suggestions for removing the y-pipe and where I can find info on order/torque specs for head and cylinder bolts?

 

[Giver800]

Yes that hose is for your rave valves. It should go to a T. Like the one in my picture.


Also for the y pipe bolts I use a ball hex head tool like the one in the picture it makes things so much easier.


Lastly I would pull the carbs off to clean them even if it is a pain as a plugged jet could very well be the cause for your low compression on the one side. Its not too hard to pull out it just can be time consuming. Just pull all the plastics off and the upper and lower air boxes and it should give you the room you need to pull them out.

Hope that helps.

 

[Giver800]

Also this link should give you all the info you need for torque specs and sequence.

https://www.snowandmud.com/ski-doo-xp-sleds/75627-2008-torque-spec-sequence.html

 

[Sekeith]

Thanks Giver800! Since I haven't taken the head off yet I'll go ahead and pull the carbs to clean em up and test my compression just to be sure. I took a quick look at the pistons and rings through the rave valve holes and they seem fine, but I suppose that can be deceiving.

Should I bother getting a tee and reconnecting the rave valves? I did some research and it seems like the solenoids tend to go and that's why most people try to bypass them (assuming that is the case here since the raves are connected together only).

 

[Giver800]

Thanks Giver800! Since I haven't taken the head off yet I'll go ahead and pull the carbs to clean em up and test my compression just to be sure. I took a quick look at the pistons and rings through the rave valve holes and they seem fine, but I suppose that can be deceiving.

Should I bother getting a tee and reconnecting the rave valves? I did some research and it seems like the solenoids tend to go and that's why most people try to bypass them (assuming that is the case here since the raves are connected together only).

Interesting, I have never heard of guys bypassing them. If it was my sled I would probably reconnect them back to how it was from factory but that's not to say that's the way you should do it necessarily. Hopefully someone with more knowledge or experience of bypassing the solenoids will chime in cause I don't really know.

Also if you haven't already put the rave valves back in you should clean them up and try to get rid of the carbon build up while you have them off.

 

[brian h]

i also havent heard of guys bypassing them,i would clean and re-hook up

 

[Sleeper700]

I got Deano at mad motorsports to modify my rave valve setup to work like the older engines. The solenoid setup fails more often than most think. It also opens the valves up later than it should. Your engine may have this type of mod.

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[Sekeith]

Any idea what the mod involves? Looking at my rave setup it seems like the fittings for the hoses were just connected together eliminating the tee, but maybe the raves themselves were changed or modified.

I'm thinking I'll sort out the low compression first then deal with setting up my raves properly since it was running fine before I lost compression on one side.

 

[Sleeper700]

I'm pretty sure that he drilled something in the cases so they worked on straight vacuum, instead of the solenoid setup.

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[Sekeith]

Reviving my old thread. I finally got around to pulling my motor apart and found that the low compression side had a bad piston ring and piston. Going to go with the wossner piston kit since that's what the guy at MOTS machining recommended to me. I'd appreciate some thoughts on piston kits if anyone has some?

Also how would I decide if the cylinder needs to be replaced? It's got a tiny bit of scoring but doesn't seem to bad. I know you guys said it's a nicaseal so no honing but there might be a way to polish it up? Was hoping to not have to replace it but now's the time to do it if it needs to be. I'll try to post pics later tonight or tomorrow.

 

[teeroy]

Reviving my old thread. I finally got around to pulling my motor apart and found that the low compression side had a bad piston ring and piston. Going to go with the wossner piston kit since that's what the guy at MOTS machining recommended to me. I'd appreciate some thoughts on piston kits if anyone has some?

Also how would I decide if the cylinder needs to be replaced? It's got a tiny bit of scoring but doesn't seem to bad. I know you guys said it's a nicaseal so no honing but there might be a way to polish it up? Was hoping to not have to replace it but now's the time to do it if it needs to be. I'll try to post pics later tonight or tomorrow.

get some muriatic acid and see if the scuff is aluminum smear and is removeable. if after you try that and you can feel the scuff with your fingernail, the cylinder will either have to be rebuilt or replaced.

 

[Sekeith]

Thanks teeroy I'll give that a try. Seems like it's readily available and worth a shot.

 

[neilsleder]

Take your cylinder to mots get him to give your cylinder a quick hone, and he can fit your rings to your cylinder. The wossner piston are great. I had then along with a rk tech head and my sled pulled!


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[tex78]

Also get Tom to measure cylinder to piston fitment, if cylinder hole is too big ( wore out) then do it right the first time