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
-
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
-
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)
-
That looks like a cut down Triumph/BSA Triple air filter.
-
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.
-
Have a look here :-
https://www.a7a10.net/forum/index.php?topic=3494.0
-
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.
-
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.
-
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.
-
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.
-
The rubber hoses are available online. Make sure to order the A7 version.
-
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?
-
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.
-
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.
-
Here are some more pictures.
-
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
-
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.
-
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?
-
That is the early A7 fitting.
-
I see it is for long stroke engine.
Thanks.
-
Here you can find a complete airfilter with battery holder for sale
https://mikesclassiccyclespares.com/product/67-4594/
-
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
-
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.
-
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
-
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.
-
Thanks Swarfy.
-
Thanks a lot Swarfy for such detailed answer.
Martin
-
I found these nice pictures today while thumbing through the Haycraft BSA Twins book
-
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.