RXL

Put a couple hundred miles on and having a blast until I heard a funny backfire in the exhaust right before I lost power ... We were running a rail line about 80-90 mph at the time and had no chance to catch it before the carnage. Left piston has a burn at the crown and the right one is thrashed.

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smokingcrater

so... are you thinking the Y-pipe split caused it? i'd think it would be the other way around. The piston rings let loose for whatever reason, and you ended up dumping raw fuel into the exhaust, where it ignited pretty much instantly. (causing what sounded like the backfire)

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1) 2000 Arctic cat ZR 700, which now thinks it is a 2001 ZR 600 EFI APV w/136" ripsaw. (for sale!)
2) 1995 Yamaha VMAX 600, which now thinks it is a Polaris! (Polaris x10 suspension, Polaris P85 clutch) (for sale!)
3) 2004 Yamaha Warrior
4) 2006 Yamaha Nytro

RXL

Yes the crack started the melt down .. Rings are intact .
The crack was more to the right side and it caused the lean burndown.. no doubt in my mind.
Have a look at the inside of the Y pipe and see how clean it is... the backfire I heard was most likely when the piston tried to glue itself to the cylinder.

smokingcrater

yeah that sucks! No way to really catch it before it happens, thermal shock probably caused it after the engine started, and then it just got worse quickly.

__________________
1) 2000 Arctic cat ZR 700, which now thinks it is a 2001 ZR 600 EFI APV w/136" ripsaw. (for sale!)
2) 1995 Yamaha VMAX 600, which now thinks it is a Polaris! (Polaris x10 suspension, Polaris P85 clutch) (for sale!)
3) 2004 Yamaha Warrior
4) 2006 Yamaha Nytro