After my first blast out yesterday at Teeside Autodrome I've need my carbs rejetting.

They are ZX9R carbs on a 1.8 zetec. Down the main striaght I saw 5500rpm in 3rd but nothing over 4K in 4th.

Nice drive up to there, no hesitation just a lack of power at the top.

I have 160 mains in, the airscrew is out 2.5 turns and the needle is in the 3rd groove up the needle. I messed about with the airscrew and needle position and these seemed to give me the best response. But, not having any bigger mains couldn't go any faster.

Any one recommend any jet sizes or other settings to get it revving?

Thanks,
Steve

Have you got access to a wideband lambda sensor??? Anything else is going to be guesswork....

Hi my engine is a 2.1l pinto on zx9rcarbs
i have 1.7 mm jets
two washers under the main needles
air screws out one turn
and the air holes in line with the needles blocked off
Bogg Brothers set them up on there rolling road
If i was you get it on a r/road before boggs set it up it was running very week at high revs / 4000 up
Jacko

PS what modle carbs have you mine are C's no clips on the needles just washers

[Edited on 22/4/08 by jacko]

Steve

I think the "air screw" is actually the Pilot Screw, which controls fueling at low throttle openings. By unscrewing it, you are exposing more of the holes, and it's enriching it at the bottom end. But beware, cause this is going to make passing the emissions tough at SVA time. If you are not getting power at 3/4 to WOT (wide open throttle) this graph would suggest it's all down to the mains.



See info on bike carbs here for a more detailed explanation:

http://www.gadgetjq.com/keihin_carb.htm

HTH

Mike

Thanks guys, Jacko, i think mine have been Dynojeted some time.

The air holes are blocked and the needles have 6 notches to move the circlip up and down.

I think they are off a later engine as they have a TPS where the earlier ones I had didn't.

Ha, cheers Mike, I've used that website before.. when I had a KLR600, you know, the one that I rode into the front of a car and thats how I came back to building the MNR? Memories... Ouch! Drilled the jet out on that too to give it more top end

carbs on manifold



These are my zx9r / e carbs i think there from a inport bike thats why thay have valves / fuel cut off's under them
Jacko

look very different to mine...

ZX9R Carbs

Another thing to check is are you gtting enough fuel in the first place?

Check the fuel pump is pushing enough fuel though. have a google on FI injection rates to work out how much fuel you need per minute flat out then see if the pump with filter can achieve this by timing how long it takes to fill a 1ltr bowl.

Regards Mark