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Discussion Starter · #1 ·
Hello, just want to say that I don't post here very often, mostly because I do not have the knowledge to answer the questions as well as the many great members on the forum, but I do read the posts almost every week and always learn something new. Thanks for that. So heres my story:

Last time I really posted was three winters ago. I had just bought my sled and ended up overheating it and leaked coolant from the base gasket into the cylinders. At this time I sent the bottom end over to Big John to get a new crankshaft put in and have the cases bored out to resolve the bearing issues that the 2007's had. I went out on a bit of a whim and ordered a top end kit and new cylinders from a company I found on Ebay called Snow-X. Everything seemed to go back together well and has been good for just over 2000 kilometres and two seasons, until today. I warmed up the sled as usual and was driving into the riding area, after about 7 KM's of mellow riding I decided to hit the ditch, ended up almost getting stuck and had to punch it for a few seconds to get out, right as i was on my way out I heard some noises from my clutches and shut the sled down. My belt had begun to rip to pieces, losing a good amount of the cords. Belt shrapnel was everywhere in the engine compartment. However the belt was really bad so I immediately put on my spare. We continued to ride and less than a kilometre later my sled just shut down at around 6000 rpm, no warning whatsoever. Before even attempting to restart it I pulled the plugs and checked for spark and see if anything else was noticeably different. The PTO plug looked a bit oilier than the MAG side, but still pretty good. Then I had my friend pull over the engine and we both agreed that the PTO side wasn't pushing too much air out of the plug hole, but there was definitely something, not a total loss of compression. I decided to try to start it, it fired up after a few pulls, but was backfiring and idling real low and needed throttle to stay alive so I shut it down and we towed it home. Took it apart right away (I know, I really need to get the equipment to do leak down tests) and as i took off the exhaust a piece of piston ring falls out. Upon getting it fully torn apart it is pretty clear that a chunk of piston ring on the PTO cylinder fell out, ruining the cylinder and the RAVE valve in the process before spitting itself into the exhaust. Heres some pictures of the carnage.

photo 1-5.JPG

photo 4.JPG

photo 3-3.JPG

Sorry for the long story, but here are my questions that maybe some experienced guys can shine some light on my situation:

- Could ingesting a piece of belt cord into the engine cause such a catastrophic ring failure or was this just a coincidence that it happened so shortly after? Engine was fully warmed up, trails were pretty hard, scratchers down, but no overheating. How does the head look? Why do you think the side that failed is oilier or could that be some of the piston material? Spark plugs have always looked the same when I pull them, running 35:1 pre mix.

- I measured my crank runout tonight and came up with .0011. It's a little higher than I thought it would be after sending the engine away so recently, but still well within Doo spec. I did however notice little TINY bits of metal shavings in the PTO side of the case, obviously from the damaged pistons. The piece of ring I took out of the exhaust matches perfectly with the missing piece on the piston so there aren't any big chunks floating around anywhere. I poured some oil into the case several times and turned the engine over by hand a few times followed by vacuuming out the oil. I did this 4-5 times and am not really seeing any metal shavings any more. Is this an appropriate way to flush the crank case?

- Who makes a solid top end kit that I can just drop in? Last time I installed a top end I only measured ring gap and piston to wall clearance, not base gasket squish etc. I just used the base gasket supplied with the kit.

- I have a set of cylinders from a 2008 XP parts sled with unknown kilometres, the cylinders look good, can still see lots of the cross hatching but minor vertical scuffing on one of them but nothing that can be felt. Will roughening up the surface with a scotch brite pad be enough? Also going to swap heads as my head has a bit of damage from my original rebuild.

Sorry for the long read, just hoping to shine some light on the situation. Cheers!
 

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Mag side head showing damage while pto piston failure?
 

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Discussion Starter · #5 ·
After investigating again this morning I think that Sledrocks is onto something. It was tough to tell through the damage but the ring was definitely 90 degrees from where it was supposed to be and the locating pin was missing. Do you think this could be attributed to the piston manufacturer or belt dust? I do use the stock intake but have the holes on the back covered by screen. The damage to the MAG side of the head was from the original rebuild, it had been smoothed out and both cylinders had the same (132) compression since then.
 

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After reading some reviews went ahead and ordered a SPI dual ring piston kit, do you think flushing the crank case out with oil multiple times is sufficient? I cant see any flakes anymore and am pretty confident because I pulled the piece of missing piston ring from the exhaust. How about the used cylinders I plan to drop in? Many people have seemed to be successful with roughening them up with a green scotch brite pad.

Still a little unsure of WHY this happened after 2000 KILOMETRES! SHould I be speaking to the people that sold me the kit?
 

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Its not uncommon to loose a locator pin and spin a ring. Could be defective piston or slight detonation that caused that. Also hard to tell from pics but it doesn't look like there is enough wash on your piston crown, appears lean??

Usually flushing the case out with oil is sufficient enough to get all debris out.

As for cylinders, I would always recommend a light hone as it makes a fresh crosshatch that is almost guaranteed to seat rings properly and in a timely fashion. Scotchbrite pad removes the glaze exposing the remaining crosshatch but isn't always a good option, depends on cylinder wear.

Take your time with the rebuild, check rods, runout, and do a leakdown once back together. It could save you from having to rebuild it again.
 

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Discussion Starter · #8 ·
Thanks for the great replies Old Hat, I believe when I installed boyesen reeds that I dropped the main jet one size, other than that jetting is stock. I am running 35:1 pre mix, should I maybe tone it back to 32:1 again? Bottom end seems good still after Big John's fix, .011 runout, everything seems tight still. As for honing, should I bring it to a shop to get done, or can I buy a hone for my drill for the future?
 

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I would do 32:1, easy to mix when you have either a powerade or Gatorade bottle. If you build lots of engines buy a hone, if not take it to a 2s shop and have them use a diamond hone. If your crank is good and leakdown test is good then you need to do "throttle/plug chops" to confirm you aren't running lean at different throttle positions. IMO the piston crowns say "lean" with the lack of wash.
Piston wash is used as an average and is very good to determine if you should enrich or lean the needle jet to achieve optimum running conditions.
 

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Discussion Starter · #10 ·
Here are the pistons, top is PTO. Piston wash is new to me, but from my limited research I can definitely see that it is lean. I will up my mixture this time round. Perhaps I should go back to the main jet size that came stock before putting in the Boyesen reeds? Or should I make one change at a time?

photo.JPG
 

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Discussion Starter · #12 ·
I have 470 mains on the shelf, was that stock? Going to take the carb apart today to clean, I haven't adjusted the needle position from stock i believe, but will make sure. What was stock needle position? Is that a good position to stick with?
 

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Discussion Starter · #14 ·
Yup needles were in the stock position, put my 470 mains back in, fuel screws have been at 1.75 turns out and running good.

Went to start putting everything back together today and turns out I was sent the wrong caged needle bearings with the kit. When I spoke to the guy on the phone he was confirming my model, it is a 2007 Summit Adrenaline 800r, he told me that he needed to know because the X models use a different needle bearing. This is new to me, has anyone heard that? Anyways, it turns out the ones he sent me are smaller, so are the wrist pins, and so is the bore on the pistons themselves. Will he be able to send me different needle bearings that make up for the smaller diameter on the wrist pins, or is this entirely the wrong kit?
 

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Hello, just want to say that I don't post here very often, mostly because I do not have the knowledge to answer the questions as well as the many great members on the forum, but I do read the posts almost every week and always learn something new. Thanks for that. So heres my story:

Last time I really posted was three winters ago. I had just bought my sled and ended up overheating it and leaked coolant from the base gasket into the cylinders. At this time I sent the bottom end over to Big John to get a new crankshaft put in and have the cases bored out to resolve the bearing issues that the 2007's had. I went out on a bit of a whim and ordered a top end kit and new cylinders from a company I found on Ebay called Snow-X. Everything seemed to go back together well and has been good for just over 2000 kilometres and two seasons, until today. I warmed up the sled as usual and was driving into the riding area, after about 7 KM's of mellow riding I decided to hit the ditch, ended up almost getting stuck and had to punch it for a few seconds to get out, right as i was on my way out I heard some noises from my clutches and shut the sled down. My belt had begun to rip to pieces, losing a good amount of the cords. Belt shrapnel was everywhere in the engine compartment. However the belt was really bad so I immediately put on my spare. We continued to ride and less than a kilometre later my sled just shut down at around 6000 rpm, no warning whatsoever. Before even attempting to restart it I pulled the plugs and checked for spark and see if anything else was noticeably different. The PTO plug looked a bit oilier than the MAG side, but still pretty good. Then I had my friend pull over the engine and we both agreed that the PTO side wasn't pushing too much air out of the plug hole, but there was definitely something, not a total loss of compression. I decided to try to start it, it fired up after a few pulls, but was backfiring and idling real low and needed throttle to stay alive so I shut it down and we towed it home. Took it apart right away (I know, I really need to get the equipment to do leak down tests) and as i took off the exhaust a piece of piston ring falls out. Upon getting it fully torn apart it is pretty clear that a chunk of piston ring on the PTO cylinder fell out, ruining the cylinder and the RAVE valve in the process before spitting itself into the exhaust. Heres some pictures of the carnage.

attachicon.gif
photo 1-5.JPG

attachicon.gif
photo 4.JPG

attachicon.gif
photo 3-3.JPG

Sorry for the long story, but here are my questions that maybe some experienced guys can shine some light on my situation:

- Could ingesting a piece of belt cord into the engine cause such a catastrophic ring failure or was this just a coincidence that it happened so shortly after? Engine was fully warmed up, trails were pretty hard, scratchers down, but no overheating. How does the head look? Why do you think the side that failed is oilier or could that be some of the piston material? Spark plugs have always looked the same when I pull them, running 35:1 pre mix.

- I measured my crank runout tonight and came up with .0011. It's a little higher than I thought it would be after sending the engine away so recently, but still well within Doo spec. I did however notice little TINY bits of metal shavings in the PTO side of the case, obviously from the damaged pistons. The piece of ring I took out of the exhaust matches perfectly with the missing piece on the piston so there aren't any big chunks floating around anywhere. I poured some oil into the case several times and turned the engine over by hand a few times followed by vacuuming out the oil. I did this 4-5 times and am not really seeing any metal shavings any more. Is this an appropriate way to flush the crank case?

- Who makes a solid top end kit that I can just drop in? Last time I installed a top end I only measured ring gap and piston to wall clearance, not base gasket squish etc. I just used the base gasket supplied with the kit.

- I have a set of cylinders from a 2008 XP parts sled with unknown kilometres, the cylinders look good, can still see lots of the cross hatching but minor vertical scuffing on one of them but nothing that can be felt. Will roughening up the surface with a scotch brite pad be enough? Also going to swap heads as my head has a bit of damage from my original rebuild.

Sorry for the long read, just hoping to shine some light on the situation. Cheers!
.0011 ? don't think your reading corectly
 

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Your sled is running too lean! If you have no air leaks, go back to stock main jet.
Also I agree your piston's locator pin must have fallen out and ring spun around into the exhaust port.
I will add that running so lean may have caused your piston to heat up and weakened the pin.

Best of luck!
 

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Yup needles were in the stock position, put my 470 mains back in, fuel screws have been at 1.75 turns out and running good.

Went to start putting everything back together today and turns out I was sent the wrong caged needle bearings with the kit. When I spoke to the guy on the phone he was confirming my model, it is a 2007 Summit Adrenaline 800r, he told me that he needed to know because the X models use a different needle bearing. This is new to me, has anyone heard that? Anyways, it turns out the ones he sent me are smaller, so are the wrist pins, and so is the bore on the pistons themselves. Will he be able to send me different needle bearings that make up for the smaller diameter on the wrist pins, or is this entirely the wrong kit?
Not sure who you are getting parts from, but someone needs a head slap. All 2007 800R motors are mechanically identical.
 
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