Mikuni EFI- Butterfly or throttle valve "closed adjustment"

On my 09 Husky TE 450 I have a Mikuni EFI-

I have had it hooked up to the I/beat and it has the "power up kit" (open exhaust, intake, o2 sensor removed/ resistor installed...

My TPS was calibrated by techs with the I/beat. My question is- there is a mechanical adjustment for the Butterfly or throttle valve- a screw which adjusts the "closed throttle position" This was set by the factory and never touched in the TPS/ Ibeat adjustments. Is that something which should never be adjusted and if so how does that relate with the TPS adjustment (done with the I/beat)- my system is adjusted as if it is closed right now - could it actually be mechanically too far open or closed from the factory? Do I leave that alone- is there a proper way to adjust that? or check- is it a non -issue? because there is also the idle screw air bypass which together with the throttle opening = the end result idle.

The bike runs great everywhere- but seams a little weak right off idle- may be because the bike is simply tuned for more topend- One guy posted that he unscrewed that screw until there was no pressure on the screw from the throttle valve and then turned it in 1/4 turn. He says he had better off idle responce. Makes me think... I should look at that...

any feedback or guidance would be appriciated- I am new to EFI.


Just curious if there's any tips on adjusting the throttle valve(butterfly) on a throttle boddy. There's no spec in any service manual I can find... Yet I know there's a specific setting or standard. Maybe fully closed accept the buttlerfly should be stopped by the adjustment bolt NOT the bore?????

anyone got a second opinoun? something....please/ and thanks

does it have a idle air control valve?

sorry man,ive never even seen a fuel inejcted husky in person.

Thanks for the responce Burned- I guess any thoughts or theories would be of help, I guess this Mikuni Efi was on some suzuki quads too.

Yes- it has an idle air turnscrew- which is like a separate air circuit (used to adjust the idle)- and it has a "fast idle" knob used like a choke- which opens the same air circut to raise the idle for coldstarts/warmup.

and it has a adjustment screw for the butterly :which stops the throttle wheel- stopping the butterfly- which can be adjusted. This seems adjusted by the factory and apparently is left alone- nothing in the service manual and when Techs set adjust the TPS with I/beat software (mikuni) they don't touch the mechanical aspect of the throttle-

It just seems as though nothing should ever be assumed in spec- and it could be out of adjustment (too open or too closed) which could be corrected by the idle control valve and the electronic calibration of the TPS resulting in a "normal" and healthy idle- BUT using the idle control valve to ofset the fact that the butterfly adjusement is off seems a bandaid- if this were the case.

It makes sence that this could effect low-end throttle responce because air traveling through the idle circuit is set versus the throttle opening is not equivalent.

I guess- if I can't find an established procedure or standard- I can play with it and test- and just go back to the original if nothing shows improvement. ( I asked the guy that played with it if he NOW had a combination of a different throttle opening (less than before) and the fact that his TPS adjustment was not off- He said that the TPS only knows the Mv is less than before so it would still be concidered the zero point and therefore Closed is closed. His method was basically unscrewing the adjsutment- till it stopped opening more- and then turning the screw in 1/4 turn.

it really doesnt matter then as long as it isnt way off.

the idle air control circuit is adjustable for this reason.

as long as the tps shows 0 when the throttle is closed,thats all that matters.


That makes sense, thanks for taking the time to look at this for me:thumbsup:

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