Carb problems , Need Help ASAP

I have a big ride this weekend and levee friaday afternoon.

I just but a dynojet ket in my WR450 , 2003. along with a zyi tie fuel/air screew and the bike runes like crap. IThas a big miss in , like it's not getting gas or something. I tryed a new spark plug on top of the allready new plug and still the same, also I cleaned my carb, thinking this could help but with no luck.

No back fire's just large miss's or chops. :applause:

Thanks For Your help


Did you lose the O-ring when you installed the Zip-Ty fuel screw? :applause:

Good thinking ,but I made sure it wasn't that. O ring and washer in place

I'm going to jet down to see if that works

What jets did you change? What were the original jet size numbers and what are the new jet size numbers? Was the bike running bad befor the jet change?

Just jetted down and it's still the same.

Going to try butting the stock neddle back in. This is only big change that came with the kit.

Bike was OK before

Is your carb slide in backwards?

Good Thinking again, the slide is is right.

THe jet that I was running was a 158, but the new kit calles for a 138, I 'm going to try a 158 just to see.


if you are talking about the main jet, you should have a 165 at the least. maybe a 160 if all the original baffles and plugs are in it. 168 if you've got it in race mode. 48 pilot.

A 138 main will burn up your engine if it runs at all! :applause:

Buy the JD jetting kit and a 48 pilot! :eek:

Needle is fine. That 138 mj is your problem.

Dyno Jet uses their own jet numbering system, they do NOT correspond to factory Keihin jet numbers....

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