Jetting Question....please help

[mrbigzmotoxer]

Quick question about jetting,

I have an 04-05 450r.....I installed a stock 04-05 carb on my practice bike and now it pops really bad under decelleration. Also when you are just sitting there and give it gas.....it backifires as well. Whenever the engine decellerates, the bike backfires and pops. The power on the bike is great and it runs fine.

My question is what to do to fix this problem? Richer, leaner main jet? what else?

I increased the main jet size and it seemed to help a little bit but it's still carrying on. Any insight would be greatly appreciated! Thanks in advance!

[wykyd450R]

Sounds like the pilot jet..How many turns out is your a/f screw? You may need to back it out a bit. I am not sure how many turns out from seated is safe before the screw dont have enough resistance to keep from vibrating out. I dont think I would go much past 3 turns out. If you need to go out further, go up a size on the pilot jet.

[mrbigzmotoxer]

ok man thanks for the suggestions.....


not too familiar with stock 04-05 carbs tho.

wheres the pilot jet located at on em?

also wheres the air/fuel screw located at?


the bike has a realtively stock motor, curtis sparks exhaust, no air box lid and uni filter.

would a 185 main seem way too big for it?

[wykyd450R]

Pilot jet is inside the float bowl. Stock size is a 48. The screw is underneath the carb pointing straight up beside the float bowl. Some carbs have a brass plug covering it to keep people from tampering with it. If so, you'll need to put a small hole in it with a drill, but dont go too deep, just an 1/8 inch or less. What I did was screw a small self tapping screw into the plug a little ways, and pull on the screw with pliers to pull the plug out.

A 185 main should be a good place to start out with just an exhaust with no lid. With the current cold temps, ya might wanna go up to a 190 or so.

[mrbigzmotoxer]

thanks a lot for all of your help man. i appreciate the suggestions...i'll try them out......thanks for all your information....now i atleast know i wasnt an idiot bc i culdnt find the screw! it's covered by that plug haha

open any other suggestions also....

[wykyd450R]

No problem man...Good luck with it. :)