Mikuni vm20 vs delorto 19mm

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Mikuni vm20 vs delorto 19mm

Postby Emerica1975 » Tue Nov 15, 2022 11:12 am

I’m wondering if anyone has tried the Mikuni vm20 clamp on style carb. Mutt has mentioned he was using a 19mm delorto on a build but that a bushing needs to be machined to fit it. It looks like the Mikuni clamp on style vm 20 might just fit perfectly onto the intake spigot on a 165st. I am wondering what if any is people’s experience with this conversion.
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Re: Mikuni vm20 vs delorto 19mm

Postby pumpguy » Tue Nov 15, 2022 12:30 pm

Back in the day, my brother and I were running a '55 125 Hummer in scrambles racing and enduros.

I managed to find a flange mount carburetor that was one of a pair that came from a 2 cylinder Yamaha 250 YDS1 (or maybe YDS2) scrambler. I believe that carb was around 20MM bore size.

I cut off the original cast iron carb mount from the cylinder, then fabricated a flange for the Yamaha carb and brazed it on. Before the brazing, I opened up the passage to match the bore of the carb and adaptor flange. It worked great. Didn't even have to make any jetting changes.

With this illustration, I'm trying to make 2 points.

1) Unless you open up the passage in the cylinder to match the bore of the larger carburetor, you're not going to realize the gain the larger bore carburetor can provide.

2) Unless you feel you must keep the round clip type carb mount your cylinder has, cut the darn thing off and braze on an adaptor that will allow you to mount a bigger and better carburetor.
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Re: Mikuni vm20 vs delorto 19mm

Postby Mutt » Tue Nov 15, 2022 1:02 pm

Im running a 30mm DelLorto on my lil race bike
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Re: Mikuni vm20 vs delorto 19mm

Postby Emerica1975 » Wed Nov 16, 2022 11:03 am

Thanks for the input. I’ve been looking into other carbs to try and the Mikuni and dellorto were the two that seemed like maybe the best choices other than going with an old linkert from a 45”. The first two being the most cost effective to try.
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