Hitchcocks Forum

I've seen a few ideas for brackets to support the weight of the carburettor on 500 bullets when using a pod filter. The issue being that the carb is attached with a clamp-on rubber manifold. Without the airbox, this is all that supports the weight of the carb and filter leading to the carbs popping off or the rubber manifold splitting through engine vibrations.

After a deal of looking around, I found what I think is a pretty simple fix and as close to an "off the shelf" solution as you'll get. The only fabrication required being a piece of aluminium flat bar with two holes drilled in it and a slight twist.

I bought a rubber lined "Munsen ring" with an appropriate diameter to clamp the air filter to the end of the carb. These rings have a threaded nut built into them.


After clamping the ring on, it both holds the filter to the carb then a piece of flatbar can be attached between the munsen ring and the rear tank mounting bolt giving support to the back of the carb, preventing it moving about and over-stressing the rubber manifold.

Neat fix
That should help out a lot of 500 owner's

That's handy for those after-market carbs which don't have a lug for and extra bracket, which I'm guessing is an awful lot of them, if we exclude the flanged Amal carbs. The VM Mikunis do have a lug for this, but I see this was left off your TM Mikuni.

A.

Thinking about it, while the Munsen ring looks like it will do a good job, if someone wanted a one-piece solution, how about a P Clip (rubber lined)? I've seen them listed up to 130mm.

A look at item no. 261392800321 on a certain well-known auction web site will show the full range. 64mm looks about right to fit over your air filter sleeve.

A.

You'd need to get a 10mm hole in the end of the p-clip if you wanted to use that tank bolt.

The standard hole is (for some reason) slightly under 6mm. You then land up with a P-clip wrapped in a nice spiral round your electric drill (don't ask!).

I know exactly whereof you speak...

You COULD use a very high-tensile M6 bolt and hollow dowel in the head-steady lug on the frame...

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Where did you source the manifold from?

ssepiol wrote: ↑

Thu Dec 30, 2021 2:23 pm

Where did you source the manifold from?

Shipped from the USA along with the carb. Mikuni part number: I-VM34-200-1

A few UK places list them but didn't have them in stock

Incidentally. If you use this plate manifold, the clearance between the bolt holes and the carb mounting is very tight. Standard M8 nuts with a 13mm hex will foul the jubilee clip. I used JIS M8 nuts which have a 12mm hex and these only just give enough clearance. Might be better with allen bolts but I really wanted to use studs here.

You can get M8 flanged manifold nuts with smaller hexagons from a VW Beetle specialist, e.g.

https://www.machine7.com/product.php?xProd=12217

These have a 10mm A/F hex section which should give a bit more twiddling room.

It can get a bit awkward with these plate manifolds, I found one the right size to fit a PWK28 to a tuned 350 Bullet head, but all I could find to fit it with was a pair of 5/16" BSC cheese head screws, and even these had to have their heads reduced in diameter for a better fit in the rubber.

A.