BSA B40 WD Air filter

[louis]

Hi,

Does anyone know of an air filter element that fits in the BSA B40 WD? I can't find any original ones and my current one needs replacing.
It doesn't need to be faithful to the age of the bike, just needs to fit in and do the job.

The BSA B50 one looks similar, as does the Petter Engine one, but I'm not 100% sure, and was wondering if anyone else has had the same problem and found a good solution.
https://www.draganfly.co.uk/index.php/component/hikashop/product/11621-
https://www.stationaryengineparts.com/Petter-Air-Filter-Element-292364-for-AC1ZS-and-PAZ1-Engines.html

Thanks for any advice anyone might have 

[chaz]

https://www.britishbikebits.com/air-filter-element-bsa-b25-b50-triumph-t25-tr5t

has dimensions on the listing if it helps

[louis]

I've measured my current one and it's dimensions are:
120mm outer diameter (4.75 inches)
80mm inner diameter   (3.15 inches)
50mm depth                (2.00 inches)

If anyone knows where to find an air filter roughly this size I'd really appreciate it.
There is a little bit of play for a slightly bigger or smaller unit in all dimensions except depth (it cant be any less than 2 inches), but not enough to fit the B50 or Petter filters 

[louis]

This one by K&N seems to be the right size, if I stick a bit of foam underneath it to make it taller.
Outer Diameter: 121mm
Inner Diameter: 83mm
Height:             41mm  (Original filter is 53mm high)
I think it also fits most BSA twins if anyone is looking for filter for them.

https://www.knfilters.co.uk/air-filters/tb-0100-replacement-air-filter


I'll report back on how well it works when it arrives and is fitted.