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Discussion Starter #1 (Edited)
Hey all.

I have a 98 Indy 500 RMK that I just had an incident with. I just picked up the sled one week ago and today had it die on me before it even warmed up.

Day one after purchasing it I warmed it up slow and cruised around a local lake. Started playing in the powder a little and after tipping it on a ski I noticed a faint coolant smell. I stopped and popped the hood and notice what looked like a splat of coolant on the PTO side body panel. Not much, enough where I thought it might have been overflow or from tipping the sled. (I did notice fresh coolant in the clear lines) It never happened again that day.

The next day I puttered into the woods with it to get to a cabin and smelled a faint bit of coolant again. I didn't see anything this time and it quickly disappeared, I put on about 100 miles with absolutely no issues.

The following day I put on well over 100 miles ripping on it much harder and having a blast and never had a single issue.

Today I flooded it out several times trying to start it on choke and was able to clean the plugs and get it to start no choke giving it throttle. It took for ever! It was about 12*F if that matters. It idled like a dream for quite a while while I put tools away, plenty of 2 stroke smoke, darker and bluer. I set out across the lake at about 40 mph for a while, when I thought she was warmed up I started in with a bit more throttle and it felt under powered. Got her to about 60 and within thirty seconds it was like someone hit the kill switch. Instantly smelled a bunch of coolant. Pulled the plugs and the mag side is a perfect brown, PTO side is frosted white with coolant... I pulled the top cover off and the bolts felt a little on the loose side (MAYBE?). The gasket underneath looked new, and was not even stuck down yet. PTO cylinder was holding water and filled to the top. Mag piston looks brown and perfect, PTO piston has an oval melted indent in the center to exhaust side of the piston.

I know coolant can cause erosion on a piston right?

I would think detonation would have melted things close to the exhaust port no?

I was running ethanol free 87 octane in this thing as I thought was recommended. Do I suck?

Where would you go from here? I need the sled to be semi reliable transportation for the next 3 weeks. After that I am happy to tear into the whole engine this summer.

I wish I knew more on the history of this sled but know nothing. I think it looks like someone might have known it had an issue and sold it to me anyway. Bummer.

Should I look for air leaks? Grab a new head gasket? Bottom gasket? Check jets and needle to see how it is setup? Drain the fuel and run 91 or more? I am away from most of my tools right now, so I cant check timing. One cylinder does look perfect One definitely got hot enough to melt aluminum!



Thanks
Erik
 

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First off, welcome.

I think you have either a cracked cylinder (water jacket) or I believe if the water pump loses it's seal(s) that coolant can leak into the crankcase. This may not be the case but I would start with a complete tear down of the engine. If you don't want to go this route then maybe you could find a known, complete engine and do a swap. It may be much cheaper than having the crank and rods checked (possibly bent if you hydro locked it), new cylinder or at a minimum a hone job, piston and rings, gaskets, water pump rebuild.....the list goes on.

Hopefully you didn't pay too much for the sled but I'm sorry it went this way. Good luck and let us know what the outcome is.
 

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Discussion Starter #3
Well. I cleaned up the top end. Removed the melted aluminum from the cylinder walls, tossed a new OEM head gasket on it and I had a whopping 50psi of compression in the PTO side cylinder. Time to tear it down a bit further.
Erik
 

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Well, I just finished a top end rebuild all is much better now. However I have pulled the nose on to a snowbank and let it idle for about 30 mins to make sure I burped all the air out of the system and I drove it around the drive way for about 50 feet. I then grabbed an infrared pyrometer and noticed only at idle the affected cyclinder is reading about 75*F higher than the other at about 350*F. I feel like EGT's at idle dont really mean much, but could this be a sign of a problem? I am going to pull the plugs again for inspection as soon as the engine cools. Any ideas?

Thanks.
Erik
 
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