20 or 22 mm carb

Enginedoctor

Enginedoctor

Well-Known Member
Built a quick 108cc while I was in town for a friend. Thought I had a carb kicking around in my toolbox. Came up short. It has a later style (bearing) head, but the cam isn't anything crazy, ideally I'd like a 20mm but a 22 would work alright, I suppose. Prefer a mikuni but a good knockoff works too. Anyone have one they upsized and shelved? Let me know I'm checking eBay as well. Thanks.

Also an intake that would work along with said carb, preferably one that clears the frame to the left.
 
6

69ST

Well-Known Member
Do yourself a big favor and source a real VM20 Mikuni...plus #130, 140 & 150 main jets, #20 & 22.5 pilots.Should be a straightforward tuning exercise, from there.

Dialing-in a VM22 on anything smaller than 125cc is virtually a black art.
 
Enginedoctor

Enginedoctor

Well-Known Member
racerx said:
Do yourself a big favor and source a real VM20 Mikuni...plus #130, 140 & 150 main jets, #20 & 22.5 pilots.Should be a straightforward tuning exercise, from the.

Dialing-in a VM22 on anything smaller than 125cc is virtually a black art.
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Fair. Thanks as always for the advice. I figured 20 was as big as I wanted to go. It seems as some of the larger carbs are more common in the aftermarket.
 
6

69ST

Well-Known Member
If you are referring to chineezy ebay carbs, most of them are smaller than their nominal sizes. That's a 2-edged sword. It's saved a lotta bacon...but has also given a lot of false impressions, regarding carb sizing. IMHO, that's fine for the one-timer, for anyone who wants to really know what they're doing...not so much.

BTW, the other advantage of a real Mikuni is parts support which is readily available.

...Almost forgot, go with the hondatrailbikes 20mm intake kit. It has the desired LH turnout. With a VM20 you should be able to place the phenolic insulator at the carburetor end. Running a hot intake makes a difference, approximately 1 main jet size, based on real-world O2 numbers. And, lowering the carb as much as possible improves fuel flow from the tank.
 
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