450 carb backfire

[steffen_ex]

i put on a 450 carb and i am having a big problem with it backfireing, it runs great when its at half or full throttle but when u want it to idle it will backfire so bad that the carb will blow off of the head of the motor, what sounds like the problem? is it just to lean or to rich? what sould i do to fix it?

[2muchquad]

Its lean,try to go out on your fuel screw a turn or two.But if its idling that bad you may need a richer pilot jet.;)

[steffen_ex]

right now i have a 170 dynojet stock needle but not sure where it is placed...should be stock....and screw out 2.5 turns, i dont have the hotstart hole covered up...will that effect it?

[2muchquad]

You dont want to have any air leaks in the carb..not good,try putting a rubber cap over it with some silicone.Thats probably where your problem lies.

[steffen_ex]

ok ill make sure ill do that but do u really think that that is why it is backfiring so badly? it not bored but it does have a cam

[2muchquad]

Oh yeah.A air leak will cause a lean condition which is why you are backfiring.;)