The BSA A7-A10 Forum

Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: Martin on 26.01. 2020 18:31

Title: A7 plunger 1951, original air filtr box
Post by: Martin on 26.01. 2020 18:31
Hi, I am just doing some inspection of my "new" A7. I am not an expert in BSA yet but obviously there is air box without air filter and also battery holder is rebuild by some handy man.
I have tried to search for some pictures, ebay spare parts, but most of the motorbikes do not have any air filter at all. Also mine was running long time without any air filter. Some spare parts are available, but especially battery holder there are plenty of different spars but nowhere complete holder.
Do anybody of have still the original air filter box/battery holder? If yes please could you send me some pictures?

Thank for any recommendation.
Martin
Title: Re: A7 plunger 1951, original air filtr box
Post by: Greybeard on 26.01. 2020 19:35
The BSA A7-A10 Forum » Technical »Amal, Carburation »K&N Air filter on PLunger A10

This is for an A10; the A7 requires a slightly different air filter to carb hose, due to the lower carb height.

I bought a new battery carrier strap, (probably from Draganfly)
Title: Re: A7 plunger 1951, original air filtr box
Post by: Nourish on 26.01. 2020 20:40
That looks like a cut down Triumph/BSA Triple air filter.
Title: Re: A7 plunger 1951, original air filtr box
Post by: Martin on 26.01. 2020 20:45
Now i see that i miss one part which is inside the air box where the filter is placed. I need to search for it or create something what can be used.
Title: Re: A7 plunger 1951, original air filtr box
Post by: Nourish on 26.01. 2020 20:53
     Have a look here :-

https://www.a7a10.net/forum/index.php?topic=3494.0
Title: Re: A7 plunger 1951, original air filtr box
Post by: Swarfcut on 27.01. 2020 09:03
Martin. You are extremely lucky to have an airbox.  Most were discarded  or cut about as the fad for pancake filters took them out of use.

 The filter is basically a steel plate, with a corrugated filter medium bonded to it, as clearly seen in the link above. Esteemed member GB made a good substitute using a cut down modern filter. The air box is the same for A7 and A10, but as mentioned the rubber connector to the carb is different to take account of the heights of the differing cylinder barrels.

Swarfy.
Title: Re: A7 plunger 1951, original air filtr box
Post by: Greybeard on 27.01. 2020 10:18
That looks like a cut down Triumph/BSA Triple air filter.
Yup. You can make two filters from that one. I bought a K&N filter which can be cleaned so I gave the other half away, (to someone here?).

I got this idea from someone on another forum.
Title: Re: A7 plunger 1951, original air filtr box
Post by: Greybeard on 27.01. 2020 10:24
The filter is basically a steel plate, with a corrugated filter medium bonded to it
Not bonded. It comes off for washing. I had, (still have, I think) the original element. The metal plate has a spot welded perforated steel former to hold the filter element in position. You can see it in pic 3.
Title: Re: A7 plunger 1951, original air filtr box
Post by: Greybeard on 27.01. 2020 10:32
Maybe someone will lend you a filter backplate for you to copy. It's mostly flat but needs flanges around the edges to seal the airbox.
Title: Re: A7 plunger 1951, original air filtr box
Post by: Greybeard on 27.01. 2020 10:37
The rubber hoses are available online. Make sure to order the A7 version.
Title: Re: A7 plunger 1951, original air filtr box
Post by: spanersc on 27.01. 2020 10:42
Hi Martin.
I've studied the photos and I think that your casing is for a 'B' series bike with the aperture for the engine hose in the front face rather than the side face as per the 'A' series ones. What do others think?
Title: Re: A7 plunger 1951, original air filtr box
Post by: Greybeard on 27.01. 2020 10:48
Hi Martin.
I've studied the photos and I think that your casing is for a 'B' series bike with the aperture for the engine hose in the front face rather than the side face as per the 'A' series ones. What do others think?
Martins filter case is certainly different to my one. I put that down to it being earlier and A7.

Martin, will you take pictures of the sides please.
Title: Re: A7 plunger 1951, original air filtr box
Post by: Swarfcut on 27.01. 2020 17:48
   Yes GB, Martin's airbox , although being the correct shape (almost?) is not the right one.
 My filter is glued to the backplate and I have never risked taking it off in case the whole thing crumbles. Looks a good bit of 1950's glue, so thought it was standard. Haven't got an owners handbook, so don't know the recommended cleaning procedure. Contemporary vehicles had wire gauze filters which were usually washed in petrol and re-oiled, but washing the filter here in petrol seemed to me to be a bit risky in case the glue dissolved. So maybe the P.O. did the work with the glue.


Martin, 
      The rubber air hose connection to the carb needs to end up on the centre line, in front of the vertical frame tube. A closer look at the pictures tells me the airbox is not the  right one, and I reckon  spanerc is on the money. The correct air box has an oval aperture facing towards the oil tank, in front of the frame tube. The connector hose fits in here, then bends at  a right angle to join  to the carb.

 Yes, more pictures would help.

 Swarfy.
Title: Re: A7 plunger 1951, original air filtr box
Post by: Martin on 27.01. 2020 18:54
Here are some more pictures.
Title: Re: A7 plunger 1951, original air filtr box
Post by: Martin on 27.01. 2020 19:21
Maybe if it will only way i can rebuild it to a7 airbox. But it fit quite well to the oil tank
Thanks for your comments. Martin
Title: Re: A7 plunger 1951, original air filtr box
Post by: Greybeard on 27.01. 2020 19:47
The correct air box has an oval aperture facing towards the oil tank, in front of the frame tube. The connector hose fits in here, then bends at a right angle to join to the carb.
Same sort of design as my A10 one.
Title: Re: A7 plunger 1951, original air filtr box
Post by: Simon59 on 27.01. 2020 20:49
Here's a picture of the back of my airbox (same as Neil's - A10 plunger) together with the original Vokes air filter. Hope this helps?
Title: Re: A7 plunger 1951, original air filtr box
Post by: trevinoz on 27.01. 2020 21:03
That is the early A7 fitting.
Title: Re: A7 plunger 1951, original air filtr box
Post by: Martin on 27.01. 2020 21:36
I see it is for long stroke engine.
Thanks.
Title: Re: A7 plunger 1951, original air filtr box
Post by: S-O Skott on 30.01. 2020 14:20
Here you can find a complete airfilter with battery holder for sale

https://mikesclassiccyclespares.com/product/67-4594/
Title: Re: A7 plunger 1951, original air filtr box
Post by: Greybeard on 30.01. 2020 14:25
Here you can find a complete airfilter with battery holder for sale

https://mikesclassiccyclespares.com/product/67-4594/
It says 'Out of stock'
Also I notice this is not exactly the same shape as mine, so maybe that is for the early A7
Title: Re: A7 plunger 1951, original air filtr box
Post by: S-O Skott on 30.01. 2020 14:42
Sorry I didn't notice it was out of stock (I think I need new glasses)

BSA spareart book says spareart number 67-4597 and it looks like the one I have on my 1954 plunger, but I might be wrong.
Title: Re: A7 plunger 1951, original air filtr box
Post by: Nourish on 03.02. 2020 15:00
Ok I can't see the difference - so please somebody tell me - What is the difference between the early and the later air filter?
Cheers
Title: Re: A7 plunger 1951, original air filtr box
Post by: Swarfcut on 03.02. 2020 16:42
Martin.  Additional detail concerning my earlier recommendations. It depends if you just want something that works, or true original parts to suit the model year.

 Airbox and filter element changed over time.

  1947 Rigid frame Longstroke A7 Engine  Air box battery carrier 67-4535,  Filter 67-4545.   Connecting hose 67-4546

   The connecting hose is straight and faces forwards towards the carb. Hole in airbox faces forwards.

  1947/48 appear to be the same basic parts.

  1949 Rigid      Frame to ZA7 109                      Airbox   67-4535         Filter    67-4545 ( 2 screw Fixing)

          Rigid      Frame ZA7 110 onward               Airbox   67-4558         Filter   67-4562  (3 Screw Fixing)

          Plunger...Same as Rigid ZA7110 on.         Airbox   67 -4558         Filter   67-4562.

  1949 models continue with the straight coupler 67-4546, from 1947. Airbox hole still faces forwards.
  The filter units look to be the same basic profile, detail difference being just the number of retaining screws.

  Can't tell if there is any significant difference, other than the number of screws but chewing this over makes me think your original airbox could be made to work.

   If the bike is a 1951 A7 Plunger, then the correct airbox with the outlet facing the oil tank is the one you want, which was introduced for the A10 in 1950.  This is the airbox and filter we are  more familiar with, requiring the rubber elbow hose.

         Airbox 67-4594    Filter 67-4600 (3 Screw Fixing)      Connector Hose A7  67-4596      A10  67-4589

   Fitted to Plunger Frames, also possibly to Rigids, the catalogues are somewhat vague at this changeover point.

       Nourish, All of the above gleaned by reference to Parts Catalogues, so apologies for not researching deeply enough previously before posting. Some of these variations were new to me.

 The answer to your question isn't here, but we can see some variations exist, position of air hose, screws securing filter element and possible variations in the profile of the pressing for the airbox.

 Errors and omissions? Someone check my part numbers please, I need a lie down!


 Swarfy.

 

                                                                     

   
Title: Re: A7 plunger 1951, original air filtr box
Post by: Nourish on 04.02. 2020 07:52
Thanks Swarfy.
Title: Re: A7 plunger 1951, original air filtr box
Post by: Martin on 05.02. 2020 12:31
Thanks a lot Swarfy for such detailed answer.
Martin
Title: Re: A7 plunger 1951, original air filtr box
Post by: Greybeard on 11.02. 2020 21:54
I found these nice pictures today while thumbing through the Haycraft BSA Twins book
Title: Re: A7 plunger 1951, original air filtr box
Post by: terryk on 12.02. 2020 08:44
I have a spare airbox and battery carrier for A10 A7 that I would sell send me a message. Im in Australia.
I thought I posted pics way back some years ago of the difference between longstroke and later airboxes.