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piston burns....question

PostPosted: June 22nd, 2001, 7:50 am
by Xtreme XC
what is the difference in a piston burning up in the center vs along the exhaust port?? Both are lean conditions right?

piston burns....question

PostPosted: June 22nd, 2001, 11:12 am
by Michiganstopcat
Im not sure im right here but id say that a piston with a hole in the top was real lean and had time to soak the heat up(like a long wide open run)and one burned along the exhaust port edge not as lean maybe could even be caused by a little shot of water.good question though but not sure im right.

piston burns....question

PostPosted: June 25th, 2001, 5:15 am
by maxiracer
I've found that holes in the center of the piston indicate detonation or pre-ignition problems, burning the edge off indicates a lean fuel condition, or a poor gas/high water content problem.

piston burns....question

PostPosted: June 25th, 2001, 6:36 am
by westisbest
starting line products has an excellent book that can be ordered telling you exactly why you burnt down for almost every condition that a snowmobile will come acrossed. i think that the hole in the middle is definitely detonation especially if you burnt it down on the mag side. it tends to run richer than the pto side. if you burnt off the exhaust port side of the piston that was a lean condition.

piston burns....question

PostPosted: June 25th, 2001, 8:22 pm
by Michiganstopcat
DETONATION AND LEAN CONDITION ARE THE SAME THING.DETONATION ACCURS BECAUSE ITS TO HOT INSIDE THE COMBUSTION CHAMBER AND THE FUEL IS BURNING WHEN ITS NOT SUPPOSE TOO LIKE WHEN THE PLUGS NOT SPARKING.DETONATION COULD ALSO BECAUSED BY LOSS OF COOLANT FLOW DUE TO THE INABILITY TO COOL THE CYLINDER.MOST OF THE TIME DETONATION OCCURS DUE TO BEING LEAN.MY BUDDY BURNT A HOLE THE SIZE OF A DIME IN HIS MAG SIDE PISTON ON A ZR 600 THIS YEAR.COME TO FIND OUT IT WAS CAUSED BY A BROKEN REED PEDEL(THEM NICE V-FORCE REEDS!! WHAT A JOKE THEY REALLY ARE)I WOULD SAY HE WAS RUNNING LEAN.

piston burns....question

PostPosted: June 26th, 2001, 1:30 am
by westisbest
detonation and lean are surely not the same thing and never will be. detonation is caused be a compression problem with poor fuel and lean is a problem of fuel to air mixture. detonation causes many problems such as bent rods and small pock marks in the pistons and heads. you will never bend a rod from being to lean.

piston burns....question

PostPosted: June 26th, 2001, 9:34 am
by NorthernSkunk
Good question Xtreme, maybe we can get some good sled posts going here. Except I can't help you with this one, my cats have been flawless over the years. LOL. I'm sure maxi and some of the other brand riders will be able to handle these questions, lol. seriously I've said before I got a mechanic buddy to help me with that stuff, and I ain't about to pretend on here I know more than I do. But I do read all the answers from you who know about this stuff, so post those answers.
Maxi what would be some good ideas to make a cat faster? (fun question)

piston burns....question

PostPosted: June 28th, 2001, 2:00 am
by maxiracer
1. Threaten it with a Rottweiler, oh you mean sleds, I really don't have a lot of experiance with the ZRT's, but I feel the best money is spent on clutching, ramps, springs, helix's and gearing. I think gaining big hp is easy, getting it to the ground is the tough part, but that's just me. It all depends what you want the sled to due, go fast in a straight line, pull hard out of the corner. Build to how you want to ride! c-ya maxi

piston burns....question

PostPosted: June 28th, 2001, 3:27 am
by hugeair
I agree with westisbest. Detonation certainly is not the same as a lean condition. Detonation could be caused by a number of things. As westisbest mentioned, poor fuel and too much compression for the fuel you are running. Also, too much ignition advance. Detonation ruins can ruin an engine quicly, as can lean conditions. I would agree that the hole in the middle of the piston is probably detonation.

piston burns....question

PostPosted: June 28th, 2001, 3:37 am
by hugeair
Hey xtreme. You havin trouble with your sled? If so, was just wondering if maybe you used low octane gas and forgot to turn off the high octane switch. This could definatley give you a hole in the middle of the piston. I'm sure you are aware that the switch advances timing a bit, which can be done with premium gas. If you used crap gas with the switch on, you will have detonation problems. Just a thought!