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Discussion Starter #1
Just bought a 1996 Xcr sp thats hasnt been ran in 3 years, i got it home and it only ran on one cylinder. I took the airbox off and i had a 1995 Xcr 600 that just had the carbs done and put them on and it ran fine. I left the old gas it and just put in some dry gas in and ran it around the house, After i thought all the old gas was out i filled it up with new gas, when i was riding it down the trail and thought i would handle bar it, i got to about 100 and it shut completly off. After i let it sit for about 5 mins it started back up but back fired really bad, i changed the plugs and it ran fine. when i got it home the middle cylinder has low compression and the sled wont idle, i was wondering what caused it to shut off and then run again?

Thanks,
Ryan
 

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Well You ran it lean... The 95 stock jetting was right around 260's and the 96 XCR SP was 380, 360, 360.

Check your compression, but I think its time for a rebuild..
 

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yeah man, sounds like you fried the engine. polaris1 is correct. it shut down because it got to the point it was too lean and started to fry the motor. if you take the plugs out and shine a light down inside, roll the engine until the piston is at bdc and look at the exhaust side top of the piston. it will probalby look like it was melting away. that's what happens when its lean burn down. that is a very expensive engine to rebuild too. more than likely took out the cylinder with it. if you need more advice, just ask. -Polaris Doc
 

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Discussion Starter #4
Its only got 2526 miles on it but it seems to be running on 1 maybe 2 cylinders but i no fo sure that the midle one is F***ed but do i have to replace all the pistons or should i just do the one thats blown ?
 

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Tear it apart first and see what you need.

You could probably get away with just replacing the bad Piston/Cylinder with OEM and re-ring the other two if they are good.
 

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Discussion Starter #7
sorry computer is being gay.... but my dad wants me to replace all the pistons and i really dont wanna spend all that money cuz i just basicly stole the sled for 600 bucks and it ran perfect.... But if the cylinder is bad how much could i pick one up for?
 

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Well, if it were me, i'd tear down the entire top end. To take the middle piston off, you have to pull either the pto or mag cylinder anyways, so you might as well pull the other one off as well. only thing extra at the least, would mean a new base gasket for that cylinder. Probably not a bad idea to pull them all anyways since it was ran so lean. I would not rering the other two if they look ok. 2500 miles on a nicasil cylinder is not that much. shouldn't have to rering until about 5-6k miles. Start looking on ebay for a cylinder. But you may not need one either. Pull it apart and get an assessment for what needs to be replaced. OEM parts from the dealer are spendy, especially the cylinders. I've had good luck with parts like that off ebay, but make damn sure the nicasil is in good shape. might luck out and find a single piston, but may have to get that from the dealer. First things though would be to tear it down and see what you need. i've had good luck with this place for used stuff:
Miner's Outdoor and Recreation 1-507-583-2712
let us know what you find. -Polaris Doc
 

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Discussion Starter #9
Alright thanks guys, im taking it to this guy that has worked on my xcr's since ive had them but ill check that place out for some parts, and another question whats the compression suppose to be for the xcr sp? thanks again
 

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Congradulations.
You've just had your first melt down. As mentioned above, you ran it too lean. Lean is hot and aluminum melts at 1,300 degrees F.
It's not as bad as many people make it sound though. Melt downs are a natural part of what we do, it's part of the learning curve and it teaches a lesson not soon forgotten.

It's going to cost you a top end kit and a gasket/O-ring kit and some time. Do all 3 holes as you pretty much want to do that any time you melt one down. Get Pure Polaris pistons etc. I know they cost more, but hold one in your hand and a Weisco in the other. The Weisco is that much lighter because it has that much less materiel and so it will need much larger clearances and this creates that much more chance for piston slap etc. They expand more with temp changes and this makes them more tempermental to jetting and elevation/ambient temp changes.

Be sure to flush out your bottom end and that it's clean and free of all foriegn matter. Check your crank run out while it's apart just to be sure and also go through you main bearings with some 2 stroke oil and roll them several times. Make sure they feel smooth and tight. I think crank run out is supposed to be with in either 3 or 4 thousanths on that motor, I forget which, but the book will have that.

Measure your cylinders in 2 directions in 3 locations to look for taper and to be with in clearances set forth by Polaris. You will get tollerance numbers off the piston box or the book
Be sure to check ring end gap.

Assemble and torque EXACTLY as in the book and make sure to do them in the propper order. I like to take them all about 1/2 the poundage called for in the order in the book, and then do it again at the recomended torque. It just seems to be better that way.

Do a propper break in and don't forget 50:1 oil in the first tank.

If there is any of this that you are not comfortable with doing, Then most shops will charge about $50 to $75 an hour and it will be about 2 to 4 hours for them to do it. Just a guess as their book normally has a time for that.

I know that some people will disagree with parts of my suggestion, but it is pretty much what I would do.
At least get the gasket and O-ring kit and go through your top end to be sure. That will guide you in the right direction.
 

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I had the 680cc version of that same basic motor, the Ultra.
If memory serves correct, I was in the 140 range on all 3 holes.
You do need to be close on all 3 as well. 1 being off or all 3 all over the place are both signs to not run the motor and to find/fix the cause
 

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major mistake.those carbs are completely different.the main jets and the needle jets are different.do not just change the mains in the 1995 carbs or you will have the same problem again.the mid range will be to lean.better to use your stock carbs and go from there.i have two of these sleds and they are very finiky to run right.
 

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What Student Driver said. Spend the coin and do it right, or you'll break the motor in short time. One of the benefits of the Wiseco's if they begin to melt, they will do so gently, rather than possibly shattering like the cast pistons. But the point is, they will both burn down given the conditions. If you are going to have the cylinders re-nicked, you can go to most of the major cylinder rebuilders and they'll set you up with jugs and piston kit for roughly $600.00.

I had thought of doing exactly that, and was going to use oversized jugs with pistons brought into spec by SwainTech coating. Turns out my jugs were all re-nicked and absolutely perfectly circular in all axis. Also were near minimum spec clearance too.
 

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Discussion Starter #14
One more question... After it shut off and it started back up it pulled wicked hard but then after the first pull it wasnt so hard... i was wondering if the rings could have fried to the cylinder walls or what ? but besides that do u think that if theres not a hole in the piston that it could just be that the rings could have fried and it will only need a gasket kit and not a piston... Thanks

-Ryan
 

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it pulled over hard basically cause you fused the piston to the cyl. wall. if youre looking for some excitement theres a set of 800 cylinders floating around the forums for sale. will bolt right to that bottom end. youre spending the money anyhow, why not make it worth the dime!
 

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Discussion Starter #16
But after it started it ran fine i dont know what the hell is wrong with it cuz i just went out and ran it and it went fine.... but when i stopped it idled at like 800 rpm when its suppose to be around 1500...But my dad has a deal goin with our mechanic so i dunno ill let u know how it turns out
 

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Originally posted by Escaladeext392
[br]But after it started it ran fine i dont know what the hell is wrong with it cuz i just went out and ran it and it went fine.... but when i stopped it idled at like 800 rpm when its suppose to be around 1500...But my dad has a deal goin with our mechanic so i dunno ill let u know how it turns out
That's how minor melt downs work.
You started to melt a ring to the cylinder wall when you got too hot. Piston probably got too hot and expanded pushing it into the cylinder. Just a guess.

When you first pulled it over, you were probably skuffing the jug in that spot where the ring was stuck.
Then it formed enough of a seal to run, but to not have the same compression or to run quite the same.
The rough spots will work like sand paper and slowly (or quickly) screw you up. Broken piston skirt could be even worse and is possible.

Your dad has you on the right track going to the mechanic.
It should be done right that way.
Don't forget to put the stock carbs back on before you take the sled in.
 

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Discussion Starter #18
When i tried to start it do u think that it hurt the cylinder any when it rubbed against it becuase im not to worried about replacing pistons im worried about the cylinders
 

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very good chance of it. when you stick a piston like that in nicasil, chances are you scored the walls. let us know what you find. -Polaris Doc
 

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ohhh that nikasil, its a wonderful thing when running, but when it goes bad. man youre screwed. and yes if it stuck, which mostlikey it did. you atleast scuffed the nikasil(or however its really spelled) and itll run with a scuff, bbut just keep getting worse.
 
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