Carbon buildup/oil on one cylinder

[C-Los SD]

Hello,

It has been awhile since I've been on here. My 77 XS650 has been in storage for the past 4 years while I was stationed overseas. Prior to long term storage, I used SeaFoam to fog the the intakes, lube the cylinders, and valves. I was in the process of squirting some marvel mystery oil in the cylinders to lube the rings before I try to turn it over and decided to check them with an endoscope. The left piston is super clean, but the right piston is full of carbon/burnt oil. I did a complete engine rebuild back in 2011 with all new seals and gaskets with JE 700cc pistons, and had a machine shop do a valve job with new seals. Additional mods include VM34's, and Hugh's rephased 277 crank and cam. The engine only has 1000 miles on it, I didn't get a chance to ride much because of work. I want to get it on the road, then I might take to apart to see what's going on in the winter. Based on your experience, is it valve seals, head gasket, or rings, or too much fuel?

Right piston


Left piston

 

[JAX71224]

Pull the carbs, yer gonna want to clean them anyway, and do a compression check, then oil the cylinders and check again. That will probably tell you what ya need to know ..............

 

[TwoManyXS1Bs]

What's with all the horizontal lines in pic #1 (right) cylinder?
Almost looks like a poorly done bore job (dull bit, excessive cutting depth), insufficient honing...

 

[C-Los SD]

I wondered about the horizontal lines as well. I don't recall it looking like that when the machine shop bored them out for the 700cc pistons, but that was 8 years ago.

 

[TwoManyXS1Bs]

I suppose that they could be only blemish deep, not noticeable after boring/honing, but now discolored and revealed after break-in.

Anyway, my money's on that for your oily piston...