A10 plunger carb

[Drew Back]

Getting my motor back together went to put carb on(amal 389) and realized it wont fit..I know the 276 is what is supposed to be on there now but they are pretty costly, new around $600 was thinking about mikuni but what exact model would I need and will stock throttle cable work..I dont have the stock air filter was planning to run velocity stack..I just want something that is going to be dependable and run well,I do see some used 276 carbs for under $200 but I dont and cant assume condition for the price..

[Triton Thrasher]

If you don't care about original looks, the Amal Concentric Mk 1 is about the smallest, cheapest simplest carburettor.

Don't get a carb with a significantly bigger bore than original, if you want a bike that runs properly.

[muskrat]

G'day Drew.
Have you fitted an alloy head? As TT says a concentric will fit on a iron head plunger A10 but not an alloy head due to the intake angle.
Cheers

[Drew Back]

No it is just the standard cast iron head nothing fancy just a bummer about that 389 goes to show you can never have enough spare parts..

[wilko]

 Why doesn't the 389 fit?

[Drew Back]

The carb is to tall could never get cable in top and no clearance at rear for air cleaner/velocity stack and it sits way to close to oil bag..

[Brian]

Unfortunately the carby is a bit of a problem on the plunger models. The concentric is the easiest swap for the original 276 and even then the best you can do is a bellmouth.

You can fit a 376 Monobloc but it is a squeeze, I have one on my plunger A10.

No way would you ever get a 389 on plus they are too big in bore size anyway.

[victortrry]

I have a 1954 A10 Plunger and the concentric carb won't fit because the engine is larger dimension than the earlier engine.  A friend has a 1953 plunger and the barrel and the head are smaller in diameter.

[duTch]

 I managed to fit a 389 to my alloy head plunger, but only after truncating the top cover, and the cable was a bit ugly.
 No way could fit a decent filter, though I did try some weird shapes.
 Finally decided on the extended offset inlet tract so now can run a K&N type filter, and works ok, but also had to relocate the battery.

 Vitto, I guess your mate has the small fin barrels, and yours are big fin...?? Can't comment on that as not sure of sm/f dimensions

[Drew Back]

That is good to know I am running the thick flange jug so I guess I have to save my pennies for that new 276 carb that cost is a little less than I payed for the whole bike..OUCH!!!!!!

[wilko]

 Well I helped a friend mount a pre-monoblock today and no way were the cables and adjusters for slide and choke going to clear the top tube. We had to ditch the choke altogether and counter bore the top of the carb for a low slung tophat fitting to take slide cable to make it work. Admittedly it is a swinging arm topend but I measured both an old plunger head and the manifold seems to be the same length???     

[Metty66]

I have a 1954 A10 Plunger and the concentric carb won't fit because the engine is larger dimension than the earlier engine.  A friend has a 1953 plunger and the barrel and the head are smaller in diameter.

hi thats weird as i have a 55 plunger with 626 concentric on and it fits ok  bit tight at top with cables but starts really easily first or second kick even after laying up over winter. Just bought new 276 for originality from burlen and hoping it wont affect this aspect of the bike ....... famous last words eh!! 😕

[groily]

On this subject, would anyone be kind enough to list the settings/jets/slide they have had success with using a 626 Mk 1 Concentric on a plunger A10 (a '52 I think)?
I ask because I have just been asked (as if I would know!) by a friend who's rebuilding a basket case which has come with a concentric that allegedly 'worked fine' (don't they all). But the burnt exhaust valves suggest otherwise and the new owner is rightly concerned.
Thanks muchly in advance.

[olev]

The settings/jets/slide etc for a plunger A7 would also be much appreciated.
cheers

[muskrat]

G'day olev. Doubt if my settings will do. 1951 A7 plunger. I run a 932 with no airfilter and straight through pipes (the mufflers are empty) on mine  . 30 pilot, screw 1 turn out, #4 slide, .106 needle jet, needle bottom clip, 300 main. A7SS head with A10 valves and 357 cam. .
Cheers