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Discussion Starter #1
Seem to have developed a problem on my 1200 XLT. The Aft cylinder piston overheats, burns a hole in the exhaust side and evenually tears up the cylinder. Done this twice now (through a mechanic) but the mechanic is not sure what it could be. This has to stop and be repaired correctly but no one seems to know what is going on. Open to any discussion with anyone who may have experienced this or just knows what is going on here. Last one lasted only 1 day. Worked great after the rebuild for one day then quit coming out of the shoot on the second morning.
 

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I have a 98 1200xl and have had a similar problem twice. I bought it with a blown motor, #3 piston. The engine was disassembled when I bought it, so I didn't inspect it very closely. It only had about 80 hrs on it. I installed an sbt engine which lasted 2 seasons(probably 50 hrs). It too ruined the #3 cylinder. Upon tear down, I found the rear seal popped out. I also found a deteriated fuel pump diaphram seal on the #3 carburetor. I think this was caused by the ethonal in the gas I was using. The seal actually melted through the pump diaphram. I dont think the ski has ever back fired or been flooded with water, so I can't explain the rear sel failure, but I'm almost positive this leaned out the rear clyinder. The first engine was using the oil injection, the second was premixed. I read an article that claimed the #3 cyl. distorts as much as .004 when the exhaust is torqued down. I hope some of this helps, but I'm still scratching my head too.
 

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if it is the rear cylinder it is the cat/conv. coming apart and blocking up the exhaust. i fixed 4 with this problem this year.
 

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Discussion Starter #6
Yamaha XLT 1200 Cylinder Problems

Scot 750,
Thank for the info. This is an area no one has been mentioning. The engine is in the process of being rebuilt now. Prior to disassembly I made special flanges to pressure test the block. This showed a severe leak in the rear seal which has been suggested may cause this problem also. However, the cat converter will now be taken apart and looked at. Thanks for the info.
 

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If The Center Section Is Missing Its Bad, Replace It With The Cat D-plate And Chip Kit. It Will Pickup Some Performance As Well.
 
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