ok! so i fix mopeds, one of my buddies has a few maxi's i work on for him, i had just rebuilt the top end on his kit (Athena 60cc?) and re-mounted his exhaust, replaced pedal shaft, and cranks blah blah blah.
plug looks rich, but i dont down jet because it ran pissah.
literally i spent a hour pulling wheelie s and torquing up hills.
his setup was
Athena 60cc, port matched moderately
15 bing, 84 jet
stock 2 shoe clutch, tuned
amazing low end, mid range, topped out around 40
i had just finished installing whatever parts i sold him, and tuning his bike up, so we went for a nice ride, prob. 9 miles, took a break and let our bikes cool off, rode back, prolly 2/3rds of the way while i was blasting him, he stopped, so i turned around, when i got back to him he was on the side of the rode wailing on his bike with a sweatshirt (it was on fire). i put it out with sand. most of the shits melted (wires, fuel line/filter) weird shrapnel i later identified as e50 chucks in the street.
we get it back to my house and notice a 3 inch hole strait thru the motor.the con rod is snapped, and clearly poking outside of the crankcase. havent cracked it open, but im pretty sure everything on that motor is fucked, the shrapnel?explosion took out the carb and intake manifold too.
why? what failed? what happend?
my assumption is ... RPMS>stock crank
on the side of the rode i pulled his plug ( fresh from earlier when i replaced it) fucking perfect.