Carb manifold sizes

[Tommy90]

I recently got a new mikuni vm22 and I measured the outlet to be at 23mm diameter. The intake manifold I have on my lifan125 is 22mm wide. I know it's not much difference but I'm just curious, other than having them lined up the same size is it better to have the manifold intake side with a larger or smaller diameter hole? My thinking would be it's better to have a larger hole so not to restrict the air flow and keep the fuel and air mix in suspension. Is there something I'm not thinking of? Say for example a mikuni vm22 on a 24mm intake or a vm22 on a 20mm intake. Which is the worse set up? I'm going to make an adapter for the carb manifold connection coz they don't line up right and I'm going to put in a bushing to have the choice of installing a vm26 later if I want. This just got me to thinking about size variations and the affects they play

 

[Poboy kartman]

Short answer: Intakes should always go from smaller to larger and exhaust from larger to smaller (towards the engine.)

Yes...mix matches in size will cause turbulence and real performance problems.

 

[Tommy90]

Cheers thanks for the explanation

 

[chancer]

Also you could have asked this question on your Original Carb Manifold thread.
We like to keep everything together. I almost posted yesterdays link again.
A moderator may merge these for you.

 

[Tommy90]

Ok