help guessing what jets to order

[hatorad3]

hey guys just finished building my 400ex. did a weisco 11:1 piston (87mm 416) 450r carb, hotcams stage 2 cam,cr450 cam chain, uni filter in a custom lidless box,white bro e series slip on. she runs good the problem is the backfiring on decel which from my research so far means its lean. the carb has a 48s pilot and a 185 main three turns on the fuel screw. anyone running a similar setup could help get me in the ball park on what to get? im by no means a pro just trying to learn. thanks for your help

[CJM]

Approx a 165-170 main, order sizes from 160-175 if I were you and a 52 pilot and 2.5 turns out the fuel/air screw.

Should be quite close.

Your currently possibly too rich on the main and too lean on the pilot.

[hatorad3]

so too much fuel can cause the back firing also?

[chevymanrick]

No what he is saying you have to little fuel coming in on decel, that's what's causing your backfire

[hatorad3]

o so the bigger pilot is going to get more fuel in the there cause its backfiring when the throttles cut,which has nothing to do with the main when its closed ?

[chevymanrick]

Exactly

[JOHNDOE83]

Id leave the 185 in there if your able to rev out all the way to top rpm's without it stuttering in the peak rpm's.

[hatorad3]

i was kinda thinking that. i do alot of trail riding with a few nice straight aways so i never really keep it pinned as much as id like lol. the place i went had a 150 pilot and a 158 so i got both also picked up a 170 and 175 mains to have. cjm i pmed you on which pilot i should use and where to put the fuel screw if you knew thanks for the help so far

[TheAwesomehonda]

Originally posted by JOHNDOE83
Id leave the 185 in there if your able to rev out all the way to top rpm's without it stuttering in the peak rpm's. Your exactly right. When jetting for the main you need to put in bigger and bigger til it stumpbles when you rev it out then go down a few sizes.

[hatorad3]

so ive tryed the 150 pilot got out to 3 turns on the fuel screw still popping on decel, figured what the hell i had the 158 pilot so i tore it apart again put it in. im out two turns on the fuel screw and STILL popping on decel. wtf is going on it smells rich riding around idk what to do now

[TheAwesomehonda]

Originally posted by hatorad3
so ive tryed the 150 pilot got out to 3 turns on the fuel screw still popping on decel, figured what the hell i had the 158 pilot so i tore it apart again put it in. im out two turns on the fuel screw and STILL popping on decel. wtf is going on it smells rich riding around idk what to do now Don't you mean the main jet not the pilot?

[hatorad3]

havent touched the main yet still 185

[JOHNDOE83]

theres no such thing as a 150 pilot:ermm:

[TheAwesomehonda]

Originally posted by JOHNDOE83
theres no such thing as a 150 pilot:ermm: Exactly what i was getting at... haha

[hatorad3]

sorry your right i ment 50 and 58 pilots lol

[hatorad3]

so now that thats cleared up any ideas. o and on the carb ive already rtvd the hotstart and the hole inside the carb