Amal 276; loose jet block

[ttrand]

My ‘51 plunger A10 GF came with a 276. Ive thoroughly cleaned it and am confident nothing is blocked. New fibre washers; doesn’t leak anymore. Float level is non-adjustable, jets and settings all  appear correct. She starts from cold no problem, but wont idle or run at low rpm. The only thing I suspect is that the jet block/carb body fit is a bit loose. Jet block pushes in firmly, but once home, is a little loose, until the big nut is on. I read a post from Slymo that this looseness might create a poor seal between jet block and carb body which will intern cause the pilot circuit to fail. I’m unsure about what to do about this. Suggestions please?
Also.. Upon close inspection, I might have a carb meant for an A7. It has a 15/16 bore, not the factory 1 1/16..
My unit has a flange stamp of 276 AX/1A7, jet block is 30T, needle jet 107, main jet 170, needle clip 2, slide 6/3. Air screw 1/1/2- 2
Could this work? Ive had it running fine in the past.. I really want to keep the factory 276, eleven though I realize the concentric is a better unit!

[chaterlea25]

Hi
A loose jet block will ruin the carburation
Instead of sucking the petrol through the pilot drillings it will suck air

I do not like the 276 type carbs, they leak and I have seen more than a couple of bikes that have gone on fire when the engines spit back through the carb 

John

[ttrand]

How can I remedy the looseness?

[chaterlea25]

Hi ttrand,

I do not believe there is a way to repair the carb body economically 
It might be possible to bore and sleeve the body ? but it would be a very tricky setup to do
The sleeve would need to have holes in it to line up with the body passages
You would be very lucky to find a good secondhand body
Time to break open the piggy bank and buy a new carb

John

[a10 gf]

  I love the 276  ...that great vintage  looks.

Apart from overtickling, if well maintained and looked after, there is no reason they should leak (by design).
But negligence + bad gaskets etc, yes, trouble.

[dave55]

Hi try this company but is in UK so dont know what postage costs would be like ? Cheers dave

https://www.a7a10.net/forum/index.php?topic=14116.0

[ttrand]

Yes, Ive been on touch with Kevin already. Sounds like a great option if a sloppy throttle slide is the problem. I fear that the loose jet block is a major issue on my 276, with no real cure that I can find.. I also found out that I have the wrong 276 on my bike, so I’m headed towards buying a new 276 from Burlen, (once Ive sold a kidney!) :0

[Rex]

How loose is loose? Back in the day Grandad would have tinned the jet block to make it tighter in the body c/w rubbing off the obvious high spots with a file.
Give it a go, nothing to lose..

[trevinoz]

tt, your carby started life on a Triumph Speed Twin. The bowl is 1AT which is a seven degree type.
The BSA equivalent has the bowl mounted on the opposite side, again seven degrees.

[ttrand]

tt, your carby started life on a Triumph Speed Twin. The bowl is 1AT which is a seven degree type.
The BSA equivalent has the bowl mounted on the opposite side, again seven degrees.

Yes, I just found that out. The seven degrees is important; the L or R switch is something I can live with. Will this carb, at 15/16 deliver juice as well as the 1 1/16? Doesn’t seem like a big difference..I’m going to try tinning the jet block as suggested and fussing with it it try and get a better fit. Worth a try!

[Rex]

That's an 1/8" difference in choke size which is not inconsiderable. Maybe run the smaller one until the correct one turns up?

[Greybeard]

My A10 has it's original 276 carb and it's fine. I put a new slide and needle in when I restored the bike. The bike has a relatively low mileage for its age; it was off the road for 30 years.
I also think the 276 looks great and as long as it continues to work I will not go modern.

[Greybeard]

I do not like the 276 type carbs, they leak and I have seen more than a couple of bikes that have gone on fire when the engines spit back through the carb 

Yes. Before I had an air filter on my bike I once had a pop-back and flames which luckily I was able to subdue with a cloth. I had to repaint the oil tank. Another good reason to have the air filter fitted.

[Swarfcut]

 The Plunger airbox is the same on A7 and A10, but the rubber elbow connector to the carb is not, the difference being due to the different cylinder block heights and carb throat diameters. The mouldings look the same but will not interchange.

 I prefer the 276. The slow running adjuster screws have never seized, having a coarse thread and locknut. Not so the monobloc where perfectly good carbs are consigned to the useful one day maybe shelf when the simple task of speeding the tickover results in a sheared off adjuster, a consequence of being it becoming electrolytically bonded to the Mazak body. Brass and Aluminium being great buddies when it come to holding each other tight.

 Swarfy.