Mikuni Carb Mounting

[firebane]

So I have a Mikuni VM32 carb that I am trying to mount up to a manifold.

The issue is that the Mikuni is 38mm and the manifold is 45mm or 1.5" and 1.75". Now I could use a silicone adapter but I've read that doing this can degrade the silicone and cause it to fail.

I have found a metal adapter that could possibly work but I am trying to keep things light as much as possible and wondering if anyone has any thoughts on how to do this.

I have exhausted my google searches for something rubber based and did find 1 thing but it would cost me $28 in shipping for a small piece of rubber.

 

[Tim]

Rewind a bit - what bike are you putting this carb on?

You can buy standard carb mounts that fit the VM32 and most bikes - they're sort of standard. I have VM34's on my XS650 as an example, and the carb mounts are standard off the shelf units made by Mikuni, but you can also buy them from all sorts of places - the bolt spacing seems to be consistent.

Measure the distance between the mounting spots on your manifold. Is the intake throat of your manifold 45mm? That seems very large for a bike you are going to run a VM32 on.

 

[firebane]

This is a totally custom setup so no off the shelf stuff will work for me.

The project is a kz400 that I have swapped the dual to a single carb setup.

I've had to create a custom manifold for this hence why I need something "custom" lol.

I may have to convert from 1.75" to 1.5" and just use a straight coupler but would just rather not.

 

[teazer]

The question cannot be answered intelligently because we have no idea what you are trying to fit it on. If it's totally custom can you machine a flat face to bolt a regular Mikuni mounting flange to it? If you have created a spigot on the manifold can it be changed to match say a GT750 spigot to spigot rubber mount?

 

[firebane]

Think 1.75" OD tubing coming from the manifold to the spigot of the VM32 carb.

I want something like this but made from rubber not silicone:

 

[hillsy]

If it were me I'd go to the local auto parts store and find a suitably sized radiator hose. Cut off the amount you need and you'll have enough left for spares. As long as it's snug over the 1.75" end it'll squeeze down on the carb when you clamp it.

If you're going with a "soft" mount like this you'd probably want to have a support for the weight of the carb (maybe at the filter end). Actually, you'd probably be best off supporting the weight of the carb whichever way you decide to mount it.

 

[firebane]

If it were me I'd go to the local auto parts store and find a suitably sized radiator hose. Cut off the amount you need and you'll have enough left for spares. As long as it's snug over the 1.75" end it'll squeeze down on the carb when you clamp it.

If you're going with a "soft" mount like this you'd probably want to have a support for the weight of the carb (maybe at the filter end). Actually, you'd probably be best off supporting the weight of the carb whichever way you decide to mount it.

Hmm that could work. You don't think the rad hose would kink? As long as the carb is secured to the manifold it doesn't move at all.

 

[hillsy]

I was thinking of only having about 2" of hose so the carb would be very close to the manifold.

Not long enough to kink anyways.

 

[firebane]

I was thinking of only having about 2" of hose so the carb would be very close to the manifold.

Not long enough to kink anyways.

I was more thinking along the lines of it getting squished with the clamp.. But I'll definitely take this one into consideration to try.

 

[hillsy]

As long as the carb is secured to the manifold it doesn't move at all.

How long is the manifold? Is the air filter supported?

Most bikes with rubber mounted carbs have short inblet rubbers and airbox rubbers. The airbox is also supported so there is minimal movement of the carbs in situ.

If you just have the carb held on by the manifiold mount / rubber then you'll have problems with vibration and fatigue.