Crank Problem

[GYOGI65]

rebuilt a 2000 400ex running in april
426 wiesco piston
stage 1 hot cam
new chain and guides
valves and guides new
new clutch
basicly new top end
now has a slight rattle an will quit when running ,idle or above makes no diffrence
removed both sides turns over by hand ok thought might be electrical until last time it quit couldnt turn over with breaker bar until turned it backwards then started right up
sometimes locks and sometimes hit key and runs
should i tear down to crank or look elsewhere
please help

[GYOGI65]

TORE ENGINE DOWN FOUND CAM CHAIN TENSIONER BAD

[02440exkid]

might wont to replace the timing chain with a HD wile it's all apart

[pimpin330ex]

ive heard that people put a dirt bike chain in but i forgot what model i guess there way more heavey duty

[02440exkid]

insted of payind $90 for a hd 1 get a crf450 timing chain it's alot stronger and only $30 bucks i have 1 on my 416ex works grate