#14 Raceknuckle

Carb again ... using the two barrel Weber DCOE40 causes two problems with this bike: first it is a really fat carb and occupies lots of room on the right side. It's a problem while driving since the leg or knee is covering the stacks. Also it's a cosmetic problem because it gets crowded as the exhaust will be on the same side.
Attaching the DCOE40 on the left simply looks weird and the manifold is too short (loss of torque).
Given this I decided to use a standard upright assembly which in turn means, exchanging the DCOE40 for an IDF40 down draft carb.

Since there's no manifold for IDF40 and Knucklehead that has each barrel and tube separated up to the heads' inlet (they are all 2into1 manifolds that in the end merge both barrels) I had to design one:

I call it "TheTubes" and it cost me quite a while to create the final version. It is twisted in the lower part, because I wanted to have the inner diameter of 39mm over the complete length of the tubes (of cause right after the top flange it goes from 40mm to 39mm). The inlet port of the head is 39mm as well.

I had a polyamide prototype made by 3D printing for fitment tests:

Fits as desired, exactly between both heads:

First thought for the final manifold was to have it printed in metal, AlSi10Mg, too. But ... after some inquiries I soon dropped that idea (the most expensive offer was about the price of the complete KN93 engine!). Currently I'm searching a metal casting company that is able to sand cast or precision cast that part. Next challenge to come is machining the flanges to measure.

Cheers,
Axel