Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board First Post - A50 500 Carb question

Hello,

I recently picked up a 69 A50 to see if I can get it running again. Previous owner said it ran when he parked it 5 years ago. I pulled the carb to clean and noticed its a 930. The slide is sticking. Question…replace carb with a AMAL 930 (190 jet on now) or get a 376?

Advice welcome. Thanks in advance!

The obvious answer is to get a Concentric of the original correct size for the bike.

I think that a 69 A50 would have come with an AMAL 626 carb.

Gordo

R626 indeed

https://www.classicbritishspares.co...emier-carburetors?variant=31299373367398

Which means it won’t run very well with a 930.

The 930 body can be straightened to stop the slide sticking, but as others have already said the correct 626 would be better.
Sometimes a sticking slide is caused by oxidation during long periods of disuse. If it's only sticking lightly, spraying the slide with WD-40 or similar and working it up and down in the carb body a few times can clean that up.

The 930 should be good enough to get it running with a good clean. Pay particular attention to the idle circuit, which has a tendency to block up.

Hi DigDirt, In my opinion, you would be better off to source a 626 AMAL Concentric or 26mm Wassell Evolution for your A50. You might be able to get it to run with a 928 or 930, but it's too much carburetion and it will likely be a slug on takeoff and through the mid-range of the throttle circuit. I had a 1970 A50 for a couple of years, and it ran great with the correct 626, pulled well and was smooth and easy to start. Never ran it north of 70 mph, and am not sure it was even capable of that. Good luck and Happy New Year!
-Dave
https://www.thebonnevilleshop.com/p...l-premier-626-type-right-pn-tbs-09-0447/
https://www.thebonnevilleshop.com/p...h-t100-t100c-500-tiger-trophy-pn-r626-8/

DigDirt The Factory manual specs for the A50 626 carb are 200 Main Jet, 25 Pilot Jet, .106" Needle Jet, Needle position 2, Throttle valve 3 1/2.

Those specs are a good starting point.

Gordo

Thank you all for the response. I’ll order the correct carb.

Next up is to sort out the wiring. It’s kinda ugly. I found the basic ‘manual’ and it contains some good info on the wiring. Any other sources of information would be appreciated as this tends to be the challenging part for me.

A few pics are here. She’s not a beauty queen.. https://photos.app.goo.gl/Z1XV5dXyJtBtLABt5

Happy new year!

Brian

looks like an excellent starting point where are you in NC? i am in Belmont

Thanks. I’m in Mooresville.

It looks pretty good, really.

The Podtronics(?) regulator/rectifier fitted is a worthwhile upgrade over the original rectifier + Zener diode, and the wiring looks to be in better shape than a lot I've seen. The heat-shrink is good, as is the blade fuse. The insulated crimp connectors and electrical tape - not so much. The black wire from the Podtronics should really be fused as well. Take lots of pics of the wiring to the regulator/rectifier unit, because the wiring diagram for the rectifier will be obsolete, and the Zener wire won't be connected.

Shouldn’t the blade fuse fit further into the holder, so the holder can be closed?

On a bike with no electric starter, the ideal place for a main fuse is in a sole common return lead, close to the battery earth terminal.

Trevor and I have taken to using a mini-loom on the battery, with both the positive and negative leads fused, and running to a 'T' socket. It requires cutting the ring terminals off the bike harness and running the wires to a 'T' plug, but does give very good wiring protection and allows the battery to be removed very easily.

digdirt i think there is a group of vintage/euro riders that meets for breakfast in Mooresville

https://www.facebook.com/groups/BritBikeBreakfast/ see if they will let you join/access

I traced the wiring and marked up a diagram. See attached pictures https://photos.app.goo.gl/U5eaMov6iTWLqfCi9

Condensor single wire to each coil…is this correct?

Thanks again for all the comments!

Your modification for the condensers is more correct for the physical layout, but both are equivalent electrically. Each condenser is in parallel with a set of points.

Yep, that's correct. From memory, the condensers give up the ghost over time, and probably should be replaced. Even better, put the old ignition system in a box and replace it with an electronic ignition if you plan to keep the bike for any length of time and ride it.

The wiring as you've shown it should give spark to get it started and running.
The original part of the wiring looks to be in reasonable shape, but it would be worth replacing the insulated crimp-on spade connectors with the original style non-insulated connecters with external sleeves. Most especially, lose that exposed blue crimp-on connector on the Podtronics black wire and plumb the wire in downstream of the fuse. That's a short circuit waiting to happen.

Thanks Shane. Carb is coming Friday so I'll get to tinker this weekend. Fingers crossed.

Hi Folks,

It’s been a few months since posting. The good news…she’s running. It started first kick with the correct carb. Thank you!

Next is brakes. The front wheel spins free, but the brake is seized. The rear works, but may be incorrect. Ive included a few pictures for your ideas on what to tackle next. Suggestions welcome.

https://photos.app.goo.gl/Znh86DHDePozjPmw8


Brian

If the rear brake works, I'd leave it alone and sort out the correctness later. Someone more knowledgeable than me will know if it's correct for your year and model.

The twin-leading-shoe front brake is correct for a 1969. It's an excellent brake when properly set up. Once you've taken the front wheel off and removed the big retaining nut, the brake will fall into your hand and you can establish what has seized up ...

Lannis

+1

The only thing I can add is that it looks like a rocket 3 back wheel and brake setup. No reason why it wouldn’t work but I would be keen to check chain alignment.

The rear brake op arm is wrong, looks too long, also fitted up side down, suspect its off a different bike, it will work but may be more severe than you need. The correct brake arm has the brake rod running slightly above the axle centre to give an idea of the correct length and orientation.

Front brake, try to avoid using oil to free off, once the plate is free from the bike , if the operating arms have seized in the pivots put the brake shoes side up, make little modelling clay wells round the pivot areas and add a few drops of penetrating fluid, leave this to soak a few days.
Mop up any remains, remove the clay and get a heat gun onto the brake plate around the pivots, tap the op arms with a lump of brass to get them moving. Rinse and repeat as needed.

Once they let go , continue to strip, try to save the shoes from contamination, if they have meat left on they can be reused. Be careful, damp down any brake dust , its got Asbestos in.