melted cylinder

[jkenosh]

i bought a used vmax 4 750 and one of the cylinder is compltely melted but the other 3 look good, the guy said it overheated but i cant think why it only took out 1 cylinder, what do you guys think

[Robs96max4]

have a look at that carb i'm guessing it's dirty....

[YAMMIEGOD 3:16]

WHISHFUL THINKING ON THE OVERHEAT. TOP OF PISTON DAMAGE LIKE THAT IS DETINATION. PROBLEY DUE TO WATER IN THE GAS OR CRAP OCTANE. THOSE CYLS PAINTED BLUE ? 3:16 (yammie tony)

[fixerman519]

Is that a hauck tradmark ?

[INLINE4]

Is that thing ported..???? Maybe a cracked cylinder causing an air leak..?? Notice the nickel plated secondary helix...That has race sled written all over it...

[jkenosh]

i got no idea about the sled, the cylinders are blue. Would water and poor octane just take out 1 cylinder like that? i was half expecting to see damage across all 4, but their isnt much damage on them, and im amazed by the amount of piston material left on the cylinder sides.

[YAMMIEGOD 3:16]

NO ALL FOUR DON,T GO OUT. LOOK , I CAN,T TELL FOR SHURE HERE WHAT HAPPENED, MOST OF THE TIME, DAMAGE TO THE TOP OF A PISTON IS DETINATION. 3:16 (yammie tony)

[jkenosh]

got the topend off of her and it looks like it doesnt have too much damage, it even looks like i could hone the cylinder. i still think im going to replace it though. i was wondering if it is a stock piston?

[YAMMIEGOD 3:16]

WELL THAT CHANGES THINGS ALITTLE LOOKING AT THE SIDES. LEAN BURN DOWN. LET ME SAY YOU GOT AWAY WITH LITTLE CYL DAMAGE THATS PRETTY LUCKY. 3:16 (yammie tony)

[jminor]

awful lot of coolant in that bottom end if it was taken apart correctly..

[fastmax]

The window in the piston looks larger than stock.

[jkenosh]

i dont know the correct way to take it apart, i sucked out what coolant i could and then i took the cylinder off. im having trouble finding the culprit here, thought for sure it was the carb but it wasnt, they were as clean as could be.then i thought water in the gas but i siphon some in a mason jar and didnt see any water, i also cylinder number 4 is starting to get little dents in the top of the piston,i also had another question, do all vmax 4 come with that paper thin copper head gasket?

[YAMMIEGOD 3:16]

DUDE, GET YOURSELF A OCTANE TESTER. THATS THE CULPRIT. 3:16 (yammie tony)

[jkenosh]

yeah you are probably right. i will get her rebuilt and find out. i had one more question, is it going to hurt to run 3 cylinders with whatever porting they have and than one that is different?

[speedmax4]

yeah you are probably right. i will get her rebuilt and find out. i had one more question, is it going to hurt to run 3 cylinders with whatever porting they have and than one that is different?

I personally wouldn't do that if it has been ported. I would send the cylinder for repair even if it needs welding and nicasil plating. Tom

[YAMMIEGOD 3:16]

WHY DO THINGS HALF ASS. THINGS HAVE TO BE MATCHED. 3:16 (yammie tony)

[INLINE4]

Dude,bring the sled to someone who knows whats going on..You are totally going to waste your money doing things the wrong way..Pay someone who knows..!!

[ALLSEASONRIDER]

Dude,bring the sled to someone who knows whats going on..You are totally going to waste your money doing things the wrong way..Pay someone who knows..!!

:agree:

[mjdevries]

If other pistons are showing signs, check the jetting in the carbs... It was probably jetted lean for drag racing, and someone may have tried to ride it as a trail sled.

[jkenosh]

guys thanks for all the help, im not trying to sound cheap about the porting and the used cylinder i just dont know any better, what seems like common sense to alot of you is not common sense to me because it is not common to my enviorment, ive only gotten back into snowmobiling for three years now and ive never rebuilt a motor before, so any help would be appreciated

[speedmax4]

If we knew what area you were located that might be a member in the same area that would be willing to help you out.

[jkenosh]

i will change my profile to reflect my location, ive thought aboyut it and decided tosend the cylinder to u.s. chrome and see if the can replate it and than porting wont be a issue

[speedmax4]

Good decision to get cylinder repaired. Once you get it back together you may want to consider running 50% premium & 50% racing fuel sense its been ported. There are many threads you can find on this websight concerning the less than desirable gasoline available today. If you run into any problems just ask for help. there should be some members around your area willing to stop and help you out. Tom

[VMAX535]

Jeff, here's my $0.02.

Motor has had some work done, piston window has been opened up, there is copper coat on the gasket, if there is a single head gasket more then likely the cylinders have been lifted. measure the base gasket thickness and let us know. Take a picture of the cylinder from different angles and post. Make sure you show one from the intake side as well. The problem is definatley like 3:16 stated is detonation but why. 90 % of the time I'll agree that bad fuel will be the culprit. Other things to check are the rubber intake manifolds if the are sucking air it will cause a lean condition in that cylinder only. Also if you can measure the squish that would be useful in determining how much work has been done to the motor.

/Dan

[jkenosh]

i will get more pics, it did have 1 real thin copper head gasket whereas the base plate gaskets looked pretty thick, i might just bring it all back to stock and just ride it

[opsled]

If you're In Kenosha Wi you have a guru right in your back yard. Pete Nydahl (Nydahl Machine). He is at 8100 144th Ave in Bristol. He is just south of 50 where the old Thomson strawberry farm was. His # is 262-857-7078. He worked with and for Olaf Aaen (another back yard source) and still does machining for him. He did the crank on my 750 and is very familiar with these engines. The guy knows his shit. He is now more into boat racing but does it ALL when it comes to 2 strokes. Give him a call and bring your stuff to him to have a look at.

I took a set of nicely ported and sleved 540 cylinders to him to be bored. He took a quick look at them, commented on the high quality of the port work and asked if the head had been cut. I told him I didn't know as I had bought the engine as it was. He told me to bring the head with when I picked up the cylinders so he could measure it. He figured just by looking at the cylinder porting that the head probably had been cut .010 but he would have to measure the cylinders to be sure. His original first look with just his eye turned out to be dead on. If he can't tell you what you have going on with your engine mods knowone can.

Good Luck, Phil (opsled)

[jkenosh]

thanks phil, i got surgery to get my back fused on thursday and after that ill run it out to him jason

[opsled]

thanks phil, i got surgery to get my back fused on thursday and after that ill run it out to him jason

Call him first (to make sure he is there) and explain what you have. He will let you know what to bring.

He does outboard boat racing and isn't always around so you are best to call and set up a time with him.


Good Luck, Phil (opsled)

[Brakes]

That motor was set for race for sure.That is also a lean burn down.Been there, Done That!