Mikuni vm20 carb?

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dj.chicken1

New Member
Apr 28, 2012
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australia
idk if i am posting this in the right area but i saw a vid on YouTube with a guy running a 49cc on a Yamaha ag100 carb which is a mikuni vm20 i believe.

I have a 60cc or 70cc whatever you want to call it and i was thinking about getting one just wondering has anybody had any experience with this or herd about it also i have a reed valve kit comming soon from rock soild engines and found my carb has broken so if i am going to buy a new one why not but a good one?

any input would be great on tips or how it runs with it.

thanks Zach.xx.
 
superharry

superharry

Member
Mar 10, 2012
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Mira Loma, CA.
It might be a little big... I'm using a vm22 on my bike, with a 147cc. it's a bit much, and needed to be jetted down. The "22" is 22mm at the bore dia. engine intake port is 19mm. The "20", is measured same way. very tunable carb!
 
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ivan H

Member
Oct 8, 2011
622
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16
australia
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Seriously mate, that is too big. I have a 66cc that has a bit done to it & have VM16. Even an 18mm, unless u have ported for seriously hi rpm is big. I also have reeds on order from RSE & am expecting to have to jet a few jet sizes richer when installing them. Mikuni is a great carb,,, but like any carb, it'll only work well if it has enough intake velocity flowing thru it. Get a VM16. Cheers
 
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ivan H

Member
Oct 8, 2011
622
1
16
australia
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well there ya go,. I've been told by someone using the same reeds that I've ordered that I'll need to go down 1 jet size when addding the reeds as it'll run rich due to eliminating spitback, which'll put me at a 70" main jet that came stock with the carb. Any smaller main jet & I'd consider a smaller carb. With a 20mm venturi u'd be jetting way up to deal with low velocity. Cheers
 
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dj.chicken1

New Member
Apr 28, 2012
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australia
ok thanks for the input boys i bought about 3 differnt carbs of a yamaha ag100 which are mikuni's

i will test them out and re jet them and see how well they go i will let you guys know :)
 
Rocksolidperson

Rocksolidperson

New Member
Feb 11, 2012
56
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Australia
Ivan i agree, i run a 15.15mm dellorto, and thats plenty. Your motor would probs end up boging right out, best go with something in around 14-16
 
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ivan H

Member
Oct 8, 2011
622
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16
australia
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hi Rock Solid, yeah, unless I was porting for serious rpm I wouldnt go bigger than 16mm. If mikuni did a 15 I probly woulda got. I mean, I could get enough top end out of the NT, its just the mikuni is a lot better built & tuneable everywhere from Idle to WOT. Oh, Tony at RSE is doing me a manifold for the reeds to fit the mikuni, still with the same length, so I imagine they'll b available now. Cheers
 
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ivan H

Member
Oct 8, 2011
622
1
16
australia
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Tip. These carbs r 4 rotary valved 2 strokes or 4 strokes & have bleeder holes in the needle jet. Air enters thru these & mixes with fuel. If u have trouble tuning in the 1/4 to 3/4 throttle range, take off air cleaner & block off the drilling at the very bottom of the air intake to stop this happening. Cheers
 
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