Mikuni with individual floats: float height setting?

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Feb 27, 2008
Hi all,

I have a '75 850 Commando with a 32mm Mikuni which is giving me some grief.

I have had a lot of problems starting the bike, despite getting a good 12v at the Boyer, and having plenty of thigh-cramping compression (electric start removed by PO). Timing has been checked and it runs really well once it's going. But the advice i constantly get is to dump the Mikuni and put on some Amals.

Anyway, in the meantime i have stripped the Mikuni and cleaned out all the jets etc and replaced the needle-valve. The problem now is that the float hight seems to be too high as the bike leaks gas out of the float bowl.

So my question is: how do you measure and set the float level height when the carb has the two individual plastice floats?

Thanks for all replies!

(anyone want to swap Mikuni for Amals?)

Vancouver, BC
The float height for a Mikuni VM32 twin float is 21mm plus or minus 1mm. This measurement is taken from the carb casting face to the top of the circumference of the round plastic floats. It is fairly tricky to measure.
I think it is worth your persevering with the Mikuni. The build quality is far better than modern Amals. I have had very high wear and distortion rates on modern Amals. If you have some old original Amals then they would be worth re-sleeving etc
Thans for the reply. It isn't leaking anymore on the centre stand since i adjusted the tang slightly, and pushed the metal thingy up a bit that is held in by the needle valve so it doesn't impede the floats from shutting off the valve.

I am a bit confused as to how i would go about doing the measurement. Does the carb need to be off the bike and upside-down, with the float held on the lever? I take it you would have to judge (guess) at which point the needle valve is closed?
Thanks for the link to the Mikuni manual. I have seen it before but this time i actually had a close look for something about floats and found a short explanation with some diagrams towards the end.

Thanks again!
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