I basically had a cam tensioner fail, made my own and over torqued it until the engine stalled hard(while riding) I'm pretty sure its what turned a failed cam tensioner into a full rebuild.. Live learn I guess. The cam chain tensioner I made while waiting for the replacement. I thought I was being slick... I read about how to set tension but the more I tightened it the quieter it got so I kept going. I put a ton of tension on it and took it for a spin around the yard... It locked up hard and stalled.. Once I removed tension it ran fine but with the noise more prevalent. After talking to some people it seemed like a manual cam tensioner would solve all my problems.. I was doubtful when doing some testing so I pulled the valve cover gasket to check valves/etc. Found this.. Ugh oh Knew at this point I was in for a new head so I figured i'd start the removal of the battered one. Found this.. My finger catches the grooves. After removing the cyl I found the piston to be pretty scratched up on the intake side(where the cam/journal problems were).. No pic on that and currently where the bike sits. The crank looks good with no play(thank god). My options are as follows as I see them. Option 1 New oem head, cams, cam chain, piston, cyl, rings bringing the bike back to stock.. parts are cheap and $3-400 should do it. Option 2 New oem head, Big bore kit and the above cost about $700 Option 3 Swap in a used CBR250r engine(seem to be more prevalent than CRF250l engines) this should be pretty straight forward. low mileage engine for about $600 Option 4 Swap in a used CBR300r engine... I can get one shipped for about $800 with very low mileage. Option 1 and 3 are comparable with option 2 and 4 being comparable. I like power and i'm leaning towards at least the big bore kit since its down to the crank. The CBR300R engine fits based on research but presents a few quirks/problems. Cons. First is the lack of an Oxygen sensor bung in the head.. I also don't have a good 250l head to use If I wanted to. Gearing.. The CBR300r engine is geared higher but I think sprockets could mitigate. ECU/Wiring potential issues. I've read many people are getting warning lights from a 3 prong vs 2 prong lean bank sensor.. I would hopefully keep the CRF250l ECU if possible and run it with my EJK on the bike(either reprogrammed for 305BB or as is not sure which I need). Pros It fits! 30WHP as is with 350cc Big bore potential down the road. Easier than a rebuild. More Powa! Uncertain about current engine/leftover shavings low mileage engine sounds nice. Anything i'm overlooking about the CBR300 swap? Also keep in mind this bike is new to me and has stage 1 W/EJK and the power was just fine although I felt it could use a tiny bit more(tuning would have done it I suspect). I'm also moving to the CO rockies so more power = a positive.