Mikuni Carbs Spitting Back

[Guest Kieran]

The GSXR600 mikuni 36mm bike carbs i've got on my pinto are spitting back when I blip the throttle. The fuel is old (2 years) and im only using the standard pinto fuel pump (no regulator).

 

Is it the old fuel, lack of regulator or possibly something else?? Timing perhaps??

 

It starts and idles really smooth, and the spitting back is only when I blip it (idle fine) and totally randomn - not just one cylinder.

 

Any ideas??

 

Cheers, Kieran

Edited May 14, 2008 by Kieran

[Guest Takumi]

could be too lean when you blip the throttle open..

 

what size jets are you using? I was using 1.65mm on 34mm carbs before.

[Andi]

Hi,

 

Mine are doing exactly the same from 2 out of 4 of them, its actually worse when its cold wether I

use choke to start it or not.

[Guest Kieran]

I wonder if the pilot jets and emulsion tubes are partially blocked then??

 

Im using 1.70mm main jets. I may lift the needles a notch too, see if that helps.

 

I havent taken the car out yet, so not got it properly warm to see if its just cold.

 

Starts and idles really wll though!!

 

Kieran

[Snapperpaul]

Bike carbs are usualy gravity fed so the standard Pinto fuel pump will produce to much pressure and defeat the the float valve.

Fuel pressure regulator set to 1.5 to 2.5 psi usually sorts this out