Question about cylinder color?

[Snowbird11]

I'm tearing down a 600 with 3400 miles on it. It has been overheated but still runs well intermittently. Lately it's been struggling. I've found the PTO side of the head to be oily and black while the mag side looks dry and lite brown. I'm unsure my problem here. Is the mag side lean or the PTO side rich? It could be a fuel injector issue but with the extreme temps being close to 300° on this machine I assumed I may have trashed the top end and possibly warped the head.

Any thoughts?

 

[1madbird]

What do the cylinders look like? I would suspect that the cylinder with the dark color is damaged and burning excessive oil or the plug was fouled and it ran that way for some time.

 

[Snowbird11]

i'll know more tomorrow. i had to stop on the project but did see some scoring on the intake side of the MAG cylinder. less than what i used to see every time i opened up my dragon. the PTO side (darker head) looked clean.

i'm sure it did have fouled plugs as i went through a couple sets recently. not sure what was causing them to foul.

 

[Snowbird11]

Pto side scored on exhaust. (Y pipe still attached)

Mag side scored on intake side.

None of the scoring is deep enough to have to renic. Can't feel them with a fingernail. I'll likely just hone and put it back together. Just wanted to make sure I didn't have any other issue causing that PTO side to be rich. There were no codes so I hope a new top end and gaskets do the trick.

 

[Snowbird11]

Well looks like I found the problem. Seems the rings were letting a good bit by and pistons scored heavily. This did not show in the compression test.

Pistons are placed with their cylinders. Wrist pins are sticking out mag side of each piston.

 

[TRS]

Pressure test your oil injectors/check valves.

 

[Snowbird11]

Pressure test your oil injectors/check valves.

Unfortunately I don't have a good way to test that currently.

Just to shed some light on the history of this machine. It's always run a little rough for the last 3 years or so. I had assumed the TPS needed some adjustment and plan to look at that after the rebuild. It's prior life the sled spent some time as a fleet vehicle with short distance high load low speed applications. Was sunk in a pond once, overheated two or three times the following winter and still ran after all that. The last time I had it out to test it was earlier this winter and it ran well for about 5 to 10 miles of riding. On the way back in it began to struggle.

When I tested the compression the PTO and mag side were within one PSI of each other. Unfortunately my Lisle compression tester has always read low by about 25 or 30 psi, so it's hard to guess at the actual value I was reading but rather compare each side.

 

[TRS]

 

[NapaMatt]

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