Vmax 600 melted piston

[Dunes2006]

Hi to all, here is the story

Last week me and my friends went into a little trip with our snowmobile.

I was on my Srx, one of my friend on his Sxr and the other on my ex vmax 600 1995

and then, something went wrong, my friend on the vmax told my that the sled doesn't have
any power,like is was running on 1 cylinder, i took a look on sparks plugs and the one on the
right was hurt real bad,not the actual picture but i was like this .
we didn't know what to do so i put a new spark and made 45 km with the engine running real bad at 60km h , with cross fingers haha

Once at home we took some parts out and there is the results


I want to know what can cause this, cause i bought a new cylinder and piston, a bad carb? or....

 

[Terrence R]

How many Kms/miles on the sled? Any way to check the crank seal on that side?

 

[Dunes2006]

mm i beleive it's about 12 000 km now, and for the crank seal i don't have the sled with me, i left it at my friend parent's house at about 2h hour from where i live
but we didn't touch that, i'm a beginner in all sled mechanic

 

[Terrence R]

mm i beleive it's about 12 000 km now, and for the crank seal i don't have the sled with me, i left it at my friend parent's house at about 2h hour from where i live
but we didn't touch that, i'm a beginner in all sled mechanic

I'm fairly new to sleds too, not to 2 smoke dirtbikes though. I know now that proper carb cleaning is very important. This is a twin, right? Have you cleaned both carbs thoroughly?

 

[Dunes2006]

No not yet this season..the mechanic that was suppose too didn't have the time to check it up before the vacations..so we take a guess that the sled was running alright. And yes its a twin..and when it works..good power for the year and a lot of fun since its not really heavy

 

[super1c]

DId you let this it warm up before taking off? By the mark and grove on the side of the piston it looks to be a cold seizure. Need better pics of jug and top of piston also. But from what i see cold seizure.

 

[Dunes2006]

i always let them run about 5-6 minutes alone and the day that appened it was in the garage before we get on it,

i will have more pictures in febuary when i'll get back to it

but even my friend start in the trail, the engine sound was weird, but didn't pay attention,
the motor blew i'd say about two hours after

 

[Devilin AblueDress!]

I'm fairly new to sleds too, not to 2 smoke dirtbikes though. I know now that proper carb cleaning is very important. This is a twin, right? Have you cleaned both carbs thoroughly?

The twins aren't so bad about carbs clogging up as the triples are, completely different carb. I had a few of the 94-96 600 twins and FLOGGED the wee of them all for years and never cleaned a carb.....never had an issue. Fuel getting even crappier now though.

 

[badassbanshee]

Could be a lot of things... Dirty carbs, bad fuel, lean jetting combined with very cold weather, bad crank seal, cracked intake boot or other air leak.

I've had the same type of issue with my right cylinder on my 95 twice. It blew out a chunk of the piston and ring on the exhaust side just like yours. I ended up finding 45 pilots in mine and the needle set on the bottom (leanest) notch. Through some reading I found out these sleds have a nasty mid-range lean spot.

Any idea of your jetting and needle position? Looks like a lean out to me.

 

[Dunes2006]

i can't tell cause i don't know much about all that, my mechanic will tell me this next month
thx for the pictures and all your info it will help a lot i really like to Learning things about all this and see
that i'm not the only one with those kind of problems

 

[Dunes2006]

here is another photo of the piston in place

 

[Michigan Brad]

Look at your intake boots very well. My uncle has the same sled with 16000 miles on it. It ate 2 pistons and wound up having a cracked rubber intake boot. These sleds are old and rubber rots.

 

[Michigan Brad]

Could be a lot of things... Dirty carbs, bad fuel, lean jetting combined with very cold weather, bad crank seal, cracked intake boot or other air leak.

I've had the same type of issue with my right cylinder on my 95 twice. It blew out a chunk of the piston and ring on the exhaust side just like yours. I ended up finding 45 pilots in mine and the needle set on the bottom (leanest) notch. Through some reading I found out these sleds have a nasty mid-range lean spot.

Any idea of your jetting and needle position? Looks like a lean out to me.

Did you alter your jetting from the factory specs to smooth out this midrange lean spot? If so what did you change and is there any mods to the motor or is it stock?

 

[aleks.sanford]

Quick question, my neighbors 600 twin vmax has lost the left piston at least twice. I took apart his carbs and they are incredibly clean not sure about the jets or the mixture settings cause I don't know much about carbs, I don't have pictures either because some guy up north took the piston with him. So how do I know what kinds of jets are in the carbs and what size do I need? Also how do I tell where the needles are set and where they should be? I live in michigan at around 800-1000 feet above sea level and this season has been from around -10-20 degrees.

 

[tripplec]

I blew mine somehow. Thinking it may have been the carb lean but they're different carbs (Smart Carb system). Oil is good and runs a bit rich which is ok. Always smoke and a bit blue on startup. But she went while cruising trails. Nothing fast or high RPM's I was a bit ticked about it and will be pulling my head off to see the damage but. Its guess work at the moment. A summer job. I don't have a garage etc so I have to decide where to move it before taking it apart. Once pulled apart I can't move it easily other than dragging it with tow cable to my suv.