It looked like it was detonated looking at it with a borescope but it's just crud built up on top-it's really thick by the exhaust port. Curious about the clean spot on the intake side...any ideas?

 

The clean spot is where raw fuel enters the chamber and doesn't burn, thus washing the crap off the piston.

It's poor design of the intake port as there's little swirl there.

 

1. What kind of nasty-a#s gas are you buying?

2. You need to get the RPM's much higher, much more frequently.

 

Looks like she needs longer rides with an fuel additive more often.
And ride it like you stole it more!

 

Not bad for an older cali bike running this crap they call gas out here . Clean the heads up , dump a little gas into the ports and see how the valves /seats seal and check closely for cracks around the plug hole area . Take in the exhaust port and see if you can get a look at the valve stem too those can gall up a bit with our gas . Oh yeah replace the 2 alignment dowel bushings on the cylinders if you can , minimum get a dremel and wheel and clean them up .

 

ok will do. gonna do a valve job since it's apart now. new rings too at least if the cylinders aren't too worn. nothing to explain yet why it was running like sh/t tho so far. going to pull the front off tonight.

 

Took half the day to get the back one on yesterday, about 15 minutes tonight to do the front.