Air filter woes

[veloduke]

Hi
I have a couple of questions regarding air filters;

I have a 1977 Mototrans Road that has a fairly small circular air filter box (120mm dia. x 40mm deph) to take a round (presumably) paper filter.
Try as I might I can't find a replacement element for this. Any ideas?
Currently running without a filter; not ideal, but it's hardly dusty in the UK at the moment !

I have just acquired a 1975 250 Desmo, also without an air filter. I have looked under the right hand side panel, but part of the air filter box is missing.
Does anyone have any photos of what should be there? Again, I can't find this information.

Any help much appreciated

Cheers

Max

[Buster]

Hi Max,

K&N Filter?

IMG_7926.JPG

[JimF]

40BFB041-D5B9-4249-9C9D-1F419899951F.jpeg

Is this the round air filter box that you are referring to?

I know of an automotive air filter that fits that can perfectly. I’ll look up the part number tonight.

Jim

[blethermaskite]

Max,
I don't have an air filter on my current 250 desmo but when I had a previous one with a std filter on I remember I ended up replacing it with a cut down car filter that was the correct depth but just needed the dia. reduced, which is simple to dd with a sharp knife, then just glue the open ends together again or you can stitch the ends together with copper wire, I think the original was about 45/50mm deep and was held in place with a large 100mm ish flat cover plate and nut.
(I may well be wrong, memory is a bit dim on this,) I think I used either a 1970s bmc mini or a 1970s triumph spitfire fram filter and maybe got two filters out of the one cut down. Nigel Lacey does a K&N filter for the widecase desmo singles if you just want to buy something that will fit without messing about.
Cheers,
George

[themoudie]

Aye Max,

I attach 3 images of the MKIII air filter housing from the right-hand side of the frame. This is the same housing as that fitted to your 1975 250 desmo. Unfortunately, I do not have the circular plate and retaining nut that George refers to in his reply, or an example of the original filter that was a circular convoluted paper filter, with fexible plastic ends. I can take measurements from the air filter housing shown, if you require dimensions of the mount before purchasing an air filter (re: Nigel Lacey selling K&N air filter posted by George).

Whilst K&N pod filters are efficient, trying to squeeze one in on the MKIII frame is nigh impossible, as opposed to the single down tube narrow case frame fitment shown in Buster's image, which appears rather nice BTW.

I hope this helps.

My regards, Bill

[JimF]

In the US, this air filter is available from NAPA auto parts stores for USD $17.50.

Crankcase Ventilation Filter (Gold)
Part #: FIL 2719

I find it fits my round Del'Orto air box perfectly (pictured in my initial reply).

I seem to recall using it in my widecase's 'toolbox' air-filter housing (like the one in the prior post) too.

NWMDC.jpg

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[veloduke]

Thanks for those pictures guys, that's very helpful.
It looks like the Desmo air filter is very nearly the same as the Spanish Road one, i'll have to give it a try.

[veloduke]

Oh and I can see that a lot of my air filter box has been cut away on the Desmo , so if anyone has a spare they are willing to let go,please let me know