Keeps blowing

[akwolfman]

My father-in-laws 570 mountain keeps blowing up.
He has rebuilt it 4 times now.
He only got 300 or so miles on it brand new.
The thing just kept eating pistons even when he tried premixing the fuel.
Any hints on what to look for.

 

[Suzzy-Q]

do you guys pressure test the motor each time you rebuild? is the motor stock? have you guys changed anything else?

 

[cobbycat]

do you have a pic of the pistons? something is killing it, and maybe we can tell from the pics.

 

[WyoBoy1000]

are you checking tolerances /

 

[akwolfman]

He has check cyl pressure.
Motor is stock and he has thrown the pistons away before i have seen them.
He has put a whole top end and cyl on twicw so the specs were good as far as i know.
Will ask him more on sunday when i see him and the snogo.
Thanks

 

[spring snow hero]

you need to worry about crankcase pressure....not so much about cyl pressure. if you have a leak in the carb boot, crank seal, base gasket.....well, that is more air getting in then the carb is providing fuel for. has the jetting been checked? any chance on bad fuel? I suspect a leak over an oil problem since you premixed. remember, just because the piston goes through the bore cold, it may not when hot.......you have to check clearances.

 

[Woody67]

Arctic Cat Mountain Sleds come calibrated for 6-9k elevation. On carbed sleds it means jetting too. Make sure it has been recalibrated for your elevation.

 

[dooadew]

you need to worry about crankcase pressure....not so much about cyl pressure. if you have a leak in the carb boot, crank seal, base gasket.....well, that is more air getting in then the carb is providing fuel for. has the jetting been checked? any chance on bad fuel? I suspect a leak over an oil problem since you premixed. remember, just because the piston goes through the bore cold, it may not when hot.......you have to check clearances.

air is getting in somewhere and leaning the motor out, check the carb boots, etc.

 

[akwolfman]

Arctic Cat Mountain Sleds come calibrated for 6-9k elevation. On carbed sleds it means jetting too. Make sure it has been recalibrated for your elevation.

Will look into it and we are roughly 50ft to 100ft above sea level.
He said the adjusted it to sea level before it was shipped out.

 

[Woody67]

akwolfman if it was not changed it will blow up every time. Look at the jet chart on top of the airbox. It takes at the very least a different clip position if not a different needle and bigger main jets. this model has had issues with lean midrange especially in cold sea level enviroments even when jetted properly.

 

[akwolfman]

akwolfman if it was not changed it will blow up every time. Look at the jet chart on top of the airbox. It takes at the very least a different clip position if not a different needle and bigger main jets. this model has had issues with lean midrange especially in cold sea level enviroments even when jetted properly.

Thanks will look into it.
He was running it in -30f to 40f weather.
Just what i hate doing is messing with carbs.

 

[MtnMasher]

I would look in your owners manual and see if they have a jetting table for your elevation. That sled was set up for the mountians and since you are down at sea level it goes lean, I agree with everyone else, jetting. I doubt anything else since it probably would have been checked by the mechanics when brought in. I hope this is of some help.