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Mikuni idle problems

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I have a Mikuni flat slide carb with accelerator pump on a 2003 DZR400s with FMF system

The bike runs a bit rough at idle and hesitates when I crack open the throttle from idle

Idle sometimes hangs on decel

Fuel mixture screw at 2 3/4 turns out seems the best compromise

Over 3 turns out cures the idle hang but bike runs rougher at idle, hesitates more when revved up

I plan to strip and inspect the carby, check jet sizes .

Other than pilot jet size, what else should I be looking at for the cause of the problem

Can a worn slide cause idle problems ?

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Eddie

I dismantled and inspected the carb today.

Only thing I could find that may be causing the hanging idle problem is a worn throttle valve.

When it's closed I can move it back and forth around 1/16".

So thats the amount of wear in the slide .

Can you tell me if this amount of movement is

excessive ?

With the engine running, if I open the throttle just of idle, i can here the throttle valve slapping backwards and forward in its slides !! Sound goes away after a few seconds

The other possible causes you suggested checked out OK

Also noticed that my carb has a column of rollers down each side that the throttle valve slides over

I couldn't find a diagram online that show those rollers for a Mikuni 36mm with pumper ??

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Eddie

Since my carb is a Mikuni flat slide with pumper I assume I have a pilot air screw rather then a fuel mixture screw.

My adjustment screw is located bottom center of the carb body towards the motor.

So screwing in makes mixture richer ?

and out is leaner ?

As I previously mentioned, the bike idles best at 2 3/4 turns out, and idle hanging gets worse at less than 2 1/2 turns out.

Question: should I be looking at a bigger/smaller pilot jet to cure idle hanging

Note: I run a FMF powercore exhaust. Airbox is stock

Thanks

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From your description of the screws location, I'm going to say it's a pilot "fuel" screw, not an air screw. The positions of the screw where it idles best and where it hangs is also indicative of it being a fuel screw. So, out would be richer and in would be leaner.

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Thanks Eddie, Trailryder

I think your right, it is a fuel screw on a 36 mm mikuni pumper

So where I'm at now is the bike idles best at 2 to 2 1/2 turns out on the fuel screw but idle hanging is bad at this point.

3 turns out the bike idles (a bit rough though) and the idle hang is reduced slightly.

Is a bigger pilot jet going to fix this problem ?

Thanks

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