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D7 Mikuni vm 22 carb.
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Geoffrey25
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April 2, 2021 - 8:07 pm
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Hi all for a while now I have had a mikuni vm 22carb 2 years later I decided to try it on my 1966 d7 and to my amazement it actually works quite well but t he strange thing is that it works better in the position that is supposed to be choke rather than what should be off choke.I have stripped and cleaned the carb and every thing seems in good order it sjo u of be really as it's never really been used since I bought it new 2 years ago I think it was only something like 20 pounds.Has anyone else had and tried one of these and found a similar with the carb running better in what appears to be the choke position many t thanks Joe.

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paulkentuk
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April 6, 2021 - 11:57 am
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Hi Joe,

I'm finishing off a 125cc D1 build, (spigot/stub mount) and acquired a, ( now obsolete) genuine Mikuni VM22 stub mount carb for it approx 14 years ago. I fitted it a couple of weeks ago and the engine was started for the first time in decades.

It started easily without choke, (so the lever is horizontal) and I found both the idle and pilot screws were far too far out. Correcting that allowed me to start the bike from cold with choke, ( takes a few more kicks now ! ) and adjust it so it ticks over nicely on the pilot circuit,  but I get the odd pre detonation. However once warmed up and with the choke off, from 1/4 to 3/4 throttle the engine bogs down. Moving the needle clip from its midway position 3 incrementally up to the top notch slightly improves midrange power but not enough !

My VM22 came with a 120 jet fitting into a holder stamped 145. 

I've contacted Allen's Performance to order a couple of larger main jets, and will play about with them, and needle height to optimise the fuel mix.

I suspect you will likewise need to adjust the pilot screw setting and play around with larger main jets ?

I ordered a 'Mikuni' jet kit off fleabay, but what turned up were circular main jets with a flat head screw driver slot, rather than the 6 sided jet installed - I'm inclined not to use them now until Allen's Performance have been in contact !

Regards

Paul

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saab9002
Chandlers ford
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April 6, 2021 - 6:27 pm
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Hi everyone,

please be aware of the hex head main jet kits from ebay (China), they do seem reasonable but the thread length is approx 1.5mm shorter than the jet you take out of the cheaper Mikuni’s, mine was a #85 size and I went up to #115. The brass washer under it is quite thick and could be taken down about 0.75mm to compensate but this thread and washer are the only parts holding the inner body of the carb to the rest of it.

But I must say I am impressed by the carb, my D7 started 5th kick after quite extensive work and hadn’t run for at least 8 yrs.

Good luck with it and if you need to borrow/try any jets I could lend/post them to you.

Chris

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paulkentuk
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April 9, 2021 - 12:37 pm
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UPDATE:-

Whilst looking around Allen Performance's  site I discovered a Mikuni carb / Bike match chart, so the VM22 I have is absolutely not the right model for my D1 125, which needs a VM20.

Equally a VM22 isn't the right carb for your D7 .

You need their VM26-0241-K if you need a pancake filter to go with that, you need their 0242-K kit.

Regards

Paul

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