forced to adapt non-original filter

[Goro F]

hello
my R51/2 unfortunately does not have the original air filter which was produced by KNECHT.

I searched on the web with out success. On the major web shop the replica is not available anymore, on ebay i get in contact with a vendor but he does not sell it separately by the engine block.

the picture shows the one that is installed on my bike. It is Dell Orto F8/7, not really bad to see under the cover but it is not working well. The inlet diameter (95 mm) is fine and fit the engine, while the outlet diameter (40 mm) looks really too small. In fact 40 mm is comparable with the diameter of each air pipe carburator.

I also have some doubts about the mesh of the filter. In general when i run my bike i feel that the airflow is too low at higher rpm.

I would cut the housing of the filter to have the outlet diameter equal to the inlet diameter and also search for a different mesh of internal filter. This with the purpose to increase the airflow to carburators

do you have any opinion/recommendation?

thx in advance

PS: consider that now main jet of 85 are installed, while i realized that my bike should run with 105. The right main jets are on the way, when i will install them i assume that the situation will be worst with the filter as it is

[808Airhead]

Jeff Moore aka Vintage sales and restorations has a correct air filter he will sell you. he posted it recently on FB.

[Goro F]

thx for suggestion, i will get in contact with him!