Borbin the 🐱

With the custom air filter and new carbs, the standard intake pipes do not fit and the aluminum - rubber combination looked ugly.
Make one :)
Using a 90° and a 45° stainless steel elbow with 3mm thickness seemed to be a good start.

Don't have back purging, so some sand would just do it.

Grinding and Sanding

Polishing

Done

Before:

After:

The Mikuni carbs do not have a vacuum port to sync carbs.
Carburetor synchronization is important for a smooth running engine, and if you follow the simple steps, you can easily add a sync port to the Mikuni carbs.
The flat spot is perfect for the connector port.

I made the connector out of bronze with M4 on the outside and M3 for the cap screw. Use a 3mm or 1/8" drill bit for M4 as this material is very soft.

Depth is about 5mm.

The outside diameter of the connector is 4.5mm.

Connecting a simple vacuum gauge shows the negative pressure for each side. Use the idle adjustment screw to set for an equal value.

This is the third version of my custom air filter box for my M72 using a paper air filter C1041.

The previous version with the K&N was OK, but using a paper filter seems to work better with the Mikuni's.

Parts are ready to assemble:

Previous version with latest version:

Assembled at the bike:

The custom airfilter box needed an update. Too much air flow caused a lean mixture.
The solution is an adjustable air flow.

The tubes were made out of stainless steel, grade 304.

Changed the filter from 6" length to 5" length (K&N Filter RD-0610) to cover for the air adjustment lever.

The current airfilter box of my motorcycle is undersized. Way too small and has the wrong connection tubes to the carbs which are not symmetrical. Note the diameter getting larger towards the carbs!
The restricted airflow makes it also very difficult to dial in the correct fuel-air-ratio.

To change this, I designed a new airfilter box that takes care of all the shortcommings:

Here are some pictures of the 'making of':