Runs good only with choke

[Hondailija]

Hello everybody,
I'm new member here and need some advices from CBX experts.

I have 81 CBX with stock exhaust, just cleaned carbs with Keyster carb kit (stock sized jets). Air filter is 3 pak K&N system from Tims CBX. Everything else is stock except the air filter.

Bike starts fine and idles nicely. Motor revs up nicely when not riding. But when running the bike the motor accelerates / takes rounds fast only with choke. Without choke there is not enough power.

Problem seems to be that the motor does not get enough fuel. I have cleaned the carbs all the way and changed the carb repair kit with stock jets. Mixture skrews are out 3 1/2.

Should I use bigger main jets with K&N 3 pak filter set? I have understood that CBX is very precise concerning air filter demandings. What other thing could be the reason for this? Or instead of bigger jets is it good idea to use shim under the top of the needle to lift the needle little more up?

Thanks for help and sorry for my bad english skills...

Tuomas
Finland

[CopperCollar]

You came to the right site, guys here are good and will lead you in the right direction.

I'll assume you pulled the slow air jets out and made sure they were clean, they are very tiny...0.13 I think. I am sure some one will chime in and refresh my memory.

I have read that the CBX is sensitive to intake changes and those K&N's will affect your jetting. I'll bet you need larger jets, back out the air screws to 2 1/2 for starters and maybe shimming the needles.

Someone here has done this mod and will have the right answer to your questions.

Mike

[daves79x]

Tuomas:
Welcome. If you have the individual filters in place of the stock airbox, yes, you need to jet way up on the mains. First I'd shim the needles about .020 inch. The procedure has been described here many times. Then, more importantly, you need to go up to at least 120 on the mains, probably a little more. If your carbs are clean, and it sounds like they are, this will solve your problem. This advice should have been given to you when you bought the individual filters. Good luck.

Dave

[NobleHops]

Hello everybody,

I'm new member here...

Welcome Tuomas!

N.

[Hondailija]

Thanks a lot.

Yes I'm quite sure I got clean everything in the carbs. I tried to find a reason for bad behaviour but now you gave me the answer.

Ok, so I will change the mains and maybe use the shims.

Good and usefull forum!