07 yz450f new piston wont start?

Hi all,

just fitted new cosworth piston kit and cam chain....bike wont start.

have good compression, good spark and fuel.

every few kicks the bike backfires which gives me impression theres an ignition timing issue, however, i havnt touched anything to change ignition timing, i removed the magneto to change the cam chain but looking for any help if this is something simple that ive missed. ive tried putting tiny amount of fuel in the barrel but still nothing, doesnt make sense to me.

please can anyone help because im on the verge of buying a ktm and no1 in theyre right mind wants to do that :p lol

Hi all,

just fitted new cosworth piston kit and cam chain....bike wont start.

have good compression, good spark and fuel.

every few kicks the bike backfires which gives me impression theres an ignition timing issue, however, i havnt touched anything to change ignition timing, i removed the magneto to change the cam chain but looking for any help if this is something simple that ive missed. ive tried putting tiny amount of fuel in the barrel but still nothing, doesnt make sense to me.

please can anyone help because im on the verge of buying a ktm and no1 in theyre right mind wants to do that :p lol

Yea you have a point on the ktm.

Take off the valve cover & go back over your cam timming. Look at the book. Your probably a tooth off.

the dots are perfectly aligned with the top of the head as in the manual.ill try looking for some pics maybe it is a tooth off, didnt think of that cheers.

took the head off again one of the oil rings was bent luckily didnt scratch the barrel, compression wasnt there. jobs done now shes ready to rip :)

All it takes is one tooth off on that cam... recheck your timing. 99% of the time a bike doesnt run with a new top end is timing. So simple, but a pain.

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