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Bomber Harris:

I recently bought from MIKUNIOZ, a Mikuni VM32 conversion kit for my 1970 Honda CB450 K1, which I’ve fitted it to my bike.  However, I have a few issues:-

The bike fires up immediately and idles great, no issues there

If I open up the throttle fast (meaning revving it up during parking position) it stalls but if I open the throttle slowly, no problems

When riding the bike, it’s as if it won’t pick up from idle speed, to fast running speed, it’s just full of flat spots.

The mixture screws are set 1.5 turns out,  as the supplier specified  however, the plugs are black and sooty and so it must be running too rich.

The jets I’m running in the carbs are:-

175 Main,
27.5 Pilot,
6DH5 Jet Needle,
159 Q-0 Needle Jet.

The kit comes with a couple of spare main jets, one size up and one size down: 170 & 180. I have the clip set on the middle position on the needle ( ie the third position of five).
I’m using SUPER UNLEASED fuel, which here in the UK, is our highest available octane fuel, designated E5 and 97 OCTANE.

The bike is completely standard, a rebuilt engine using NOS parts, with new liners in the barrels, bringing the bores back to standard. Stock exhausts etc.

Has anyone in the UK fitted these Mikuni carbs to their bike? What jets did you end up using, should the clip on the needle be moved to another position? Etc.

Any information gratefully received.


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