piston melt down

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moomba1

New member
my 95 800 st keeps melting pistons i did the mixture test plugs looked good nice gray and the next day it melted down #2 and just replaced #1 cylinder and piston . is there other causes for this ?
 

moomba1 said:
my 95 800 st keeps melting pistons i did the mixture test plugs looked good nice gray and the next day it melted down #2 and just replaced #1 cylinder and piston . is there other causes for this ?
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Check your coolant. Once you put thses bad boys back together they need to be burped. Put the front end high or tilt to the left. Make sure the the rear heat exchanger is getting warm. If thetre is a air lock look out as the plugs wiil show grey!!.

I can give you a way tech reason but let us know if this helps.

/Dan
 
moomba1 said:
my 95 800 st keeps melting pistons i did the mixture test plugs looked good nice gray and the next day it melted down #2 and just replaced #1 cylinder and piston . is there other causes for this ?
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"i did the mixture test plugs looked good nice gray"
At various RPMS???

grey? what exact part/area of the plugs were grey?
can you post a close up clear pics of one or more of your plugs?

Jetting, altitude, pipes, fuel type/octane etc??

you dont have leaking exaust flanges, or other wise leaking pipes/exaust manifolds do ya?

A bit more info, and some others will probley be able to help figure this out..

AL P
 
My thoughts exactly when i read the first post, since when is grey a nice color when it comes to engines? Doesnt grey mean piston or something is wearing or melting or something NOT good? Certainly not NICE! Like mentioned above,more info, Jetting,Alt, pipes,stock or aftermarket, ETC. I would think your jetting is off,cause grey dont sound good.but it could be a number of things.
 
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YIKES...GREY...????

Like others have said!!

moomba1, check out this old link from the Max site here re: plug reading & other links to look at.

http://www.vmax4.com/vbulletin/showthread.php?t=3439&highlight=Plug+Pictures

This might help you in "reading the plugs" & as others have said, you have to narrow down what your settings currently are so that you have a bench mark to work from & trouble shoot where your issues are.:a10:

Good luck & keep us posted.

Rob
 
sorry did not say that right, the plugs are a tan the grond electrode rings are half way in the electrode . the pistons are a dark and can't see washing with a borascope. always run 91 octane gas. the sled has a pipe all the rest is stock.the #2 piston was in good shape when we had the head off. the # 2 is missing the plug is gray now and electrode is bent over.i think the piston is melting down. did not get head off yet.don't know the jetting it was at the same altatude as last year had no problrms then. the alt is 3800 feet. thanks
 
Hmmmm???

Did you clean the carbs before riding this season?

Maybe dirt in that carb leaned it out?

I know that with today's LOW QUALITY fuel, at least here in OR, ya cannot chance trying to run it without carb cleaning. Our fuel only has a documented shelf life of 6-8 weeks!!

I made that mistake once!! Fortunatley it was not the Max that suffered!!:cussing:
 
no i did not clean the carbs. i do run fuel stablizer and it war in a building all year. the pistin i replace looks like it got hot in the center it is dished. i was wondering if it could be a problem with the oil injection not running lean.
 
do those drop in fitch's work? anyone have experience?
if they do, that would prolong your fuel life by months
 
Geiger said:
do those drop in fitch's work? anyone have experience?
if they do, that would prolong your fuel life by months
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Ooh, that might be a can of worms.....:2argue: Some say yes, others say no.

IIRC there is a fiesty multi page thread at TY on the Fitch..

I personaly use piston wash as my primary diagnosis tool and then the spark plug.

This concerns me
# 2 is missing the plug is gray now and electrode is bent over
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IMO it can only mean two things. It wasn't gapped properly when installed, or something went through the cylinder/ or the piston smashed it. Did you check the white dohickywumpuses in the airbox?
 
I'm no sled mechanic but I did hear that removing the air boxes and replacing them with filters such as you have done ,even despite jetting they show lil or no problems untill you are out on the lake doing high speeds.Given the amount of air ducks and the size of them in the vmax4's there is alot of air being rammed into them and without the boxes the air cant be perfectly regulated. On a further note be kind
to your vmax and clean the carbs every year
 
if this help we drain our tanks at the end of the winter and put 10 gallons of aviation fuel which you can get at your local lil airport in most cases,and start it every month thru the summer and typically we have no problem we still check them every year but they are ussually spotless inside hope this may help someone, airplane fuel has longer shelf life then pump gas
 
My experience in racing days, if piston burns down by exhaust, it leaned out, if piston holled in the middle, coolant air locked, or really bad gap, or leaking crank seal. I done both of these multiple times, so experienced with this, yah, learned the hard way. For carbs, watch for the air bubbles in fuel line, killer as well. Rebuild fuel pump. Keep in mind this is all on a 2 cylinder 440 srx.
 
you definately need to check your carbs. as well make sure the carb boots are in good shape as well make sure you dont have water in your fuel.
 
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