5 replies [Last post]
Micha's picture
Joined: 10/12/2007
Posts: 390

I took off the air filter.
Is it possible to install a modern paper filter instead of the original mesh?
Can I extract it without disturbing the housing? And if not – can I dip the original in cleaning solution?
Is it all metal inside?

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Michael Steinmann
R51/3 1952
Engine Nr. 529466

schrader7032's picture
VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6950
I think these are

I think these are affectionately called "rock strainers"...they only keep the bigger rocks out! I have something similar on my R25/2. I haven't done it very many times because I don't ride it that often and in very controlled situations. I was told to bath the wire mesh in a mixture of 10 parts gas with 1 part oil. I recall pouring the mixture through the mesh a number of times and then let it drain/dry. That cleans it as well as leaves a coating of oil which should be able to capture bits of dust and dirt.


Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

The Plunger
The Plunger's picture
VBMWMO #8356
Joined: 09/03/2012
Posts: 252
Yes, it is designed as an oil

Yes, it is designed as an oil bath filter, meaning the moist, oil coated coil of metal captures dust and dirt(and small rocks). I've found no mention on the maintenance of it but I would think blowing it out once a year, cleaning and coating as Kurt does would suffice. You could certainly homebrew a filter out of a HVAC filter or some such. Seems to me Mr. Stafford was selling them on Ebay once. Unless you are riding in the sands of North Africa the original should do the job.
I use my original as is but I coated it with straight 30 weight. I guess I'll see how it performed come November's mothballing.


'52 R67/2

In what space, sir. In what space!?

Grant R26
Grant R26's picture
VBMWMO #8145
Toronto Canada and Long Island, Nova Scotia
Joined: 03/28/2011
Posts: 213
Hi Micha consider yourself

Hi Micha
consider yourself lucky...my first R51/3 is one of the first 200 made and used coconut fibre for a "filter" element. when I peak through the vents I see that most of it is gone. Pea-gravel would probably pass through mine now.

I found a number of eBay vendors who sell 6 x 12 x 5/8 " squares of foam filter material for dirt bikes. I gather they go through air filters every week or two.

I cut mine to shape and fished it through the holes and managed to have it cover all the intake pathways and now have that extra bit of protection. Twp years now and thousands of miles and still no hint of resistance or plugging up so I'm happy so far.

I had considered tearing it apart and replacing the coconut fiber with stainless steel scouring pad material but don't want to dismantle and worry about a single thread of this stuff making its way through the intake tubes...good grief

Stick with what you have. perhaps soak it for a few hours in Kerosene and thoroughly wash it out then oil it and use it as intended. Lots of tractors and heavy farm machinery used the same systems and you also get plenty of air via the magneto chamber too. check that filter too.

Grant in Toronto

Micha's picture
Joined: 10/12/2007
Posts: 390
Hello Grant, Thanks for your

Hello Grant,
Thanks for your post.
I will do so.
I once had an old german tractor, an Holder A12 that was equipped with such a filter!
It had an impossible 2-stroke forced air cooled Sachs single cylinder 604 ccm diesel engine.
The filter was made by Mann & Hummel and I can remember these oily instructions...


Michael Steinmann
R51/3 1952
Engine Nr. 529466

R68's picture
Joined: 08/20/2008
Posts: 467
I think...

...you have a 1952 model year only air cleaner there, in nice condition (paint aside!). I'd think that in-town it's sufficient, but if your spending time out riding in the desert, you can always just use an easy to find and inexpensive air cleaner with replaceable cartridge from an R50/2 or R60/2. These fit the R51/3. The 1952 cleaner you have is rare, and expensive, and no real point in modifying it? I didn't know they used coconut fibers in the old one/thanks!

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