Got myself a retired logging 660 to fiddle with.
Exhaust looks pretty dirty. Piston rings were sticking a bit. Low compression.
Cleaned up the piston ring grooves, applied oil, put everything back together.
Now there is some compression.
Added Red Max true fuel
Started saw, did some piss revving then saw died.
Pulled rope, flywheel just spun.
Took flywheel off. Sheared off flywheel key.
Found another key from other parts saw.
Reassembled, started up again.
Runs good. Will have to see how the saw cuts in wood.
Might still need a full tear down with a new piston and cylinder but maybe it’s just the oil the guys use which I’m not a fan of for saws.