787 pto cylinder seized??

[Codylee]

I have a 1997 challenger 1800 with the twin 787s. Was riding around at about 6k and the port engine rpms dropped to 5500 then back to 6k. Brought it down to idle and it died immediately. Got it home checked compression and the pto cylinder had zero. Mag had 150. Both had 150 last time I checked (about a week ago). I rebuilt carbs 2 weeks ago and it was running great until now. Already done a leak down test and it held. I’ve checked oil pumps and replaced oil injector lines prior to this also. Anybody got any idea what would cause this?

 

[mikidymac]

Did you clean that piston? It shouldn’t be clean and dry like that.

 

[Codylee]

Did you clean that piston? It shouldn’t be clean and dry like that.

No I haven’t touched it. It had no piston wash on it. I thought if it was lean then it would be charred black? The mag piston looks okay I thought but the pto looks like possible denotation. Not sure how though

 

[JeremyD615]

Well that plug looks terribly lean, but it doesn’t match up with the piston. Water ingestion and some major steam cleaning maybe? It’s odd for sure...

 

[Codylee]

Well that plug looks terribly lean, but it doesn’t match up with the piston. Water ingestion and some major steam cleaning maybe? It’s odd for sure...

Yeah I’m trying if figure out what happened because I got a rebuilt one I’m putting in next week and really don’t want to burn that one up.

 

[Codylee]

Some of the piston crown next to the exhaust port has actually melted away if you look closely you can see it. And also there is a crater directly below the spark plug where it started to melt the top of the piston.