2001 valve specs + backfiring

my bikes got a 2005 with a 2001 cylinder head on it, are the valve specs different for both of those years or did it stay the same, everything is in spec as far as i know, i shimmed and measured the valves a little while ago, but sometimes when i kick the bike over it will pop loudly and then take some effort to start after that, other times it starts first kick no problems. whats up?

thanks you for any replies.

the valve specs are the same for all of the 250f's. as for it popping i would think jetting... :excuseme:

Sounds like the carb is too rich. Either the fuel screw or the pilot jet.

If you know the valve clearances are correct, I'm with the other folks on jetting.

my bikes got a 2005 with a 2001 cylinder head on it, are the valve specs different for both of those years or did it stay the same, everything is in spec as far as i know, i shimmed and measured the valves a little while ago, but sometimes when i kick the bike over it will pop loudly and then take some effort to start after that, other times it starts first kick no problems. whats up?

thanks you for any replies.

The cylinder head is very different from '01 to '05. They changed the shape of the combustion chamber in '05, so both the piston and the head changed.

I'd try an '01 to 04 piston with that head.

Sounds like the carb is too rich. Either the fuel screw or the pilot jet.

If it pops it is lean.

Turn your fuel screw out a little bit. Also, something to remember is it is normal and you should have a little bit of popping on decel but if you believe it is too much then turn out your fuel screw just a little bit.

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