Amal 276 pre-Monobloc carb questions

Duncan, I don't think that the float chamber is the cause of your problem as they'll run quite happily with the lid off but obviously it should be replaced. There is not much chance of repairing 'mazac' once it's started to break down like that but a smeer of 'Devcon' or something might help.

Your chamber has a recent plastic float (and needle, I think) but the seat underneath might not be 100% despite that.

I'm pretty sure that you have identified the problem with the jet block. The Norton single should have adjusting screws on the right (sitting on the bike) which means that the small drilling in the jet block should be on the other side. However, your block looks to be left handed - i.e. it has come from a carb with the pilot adjusting screw on the left hand side. I have one of those here and I think that it came from an A7 or something.

There is a further complication in that the WD16H and Big 4 were pretty well unique in using 276 carbs as the others used the 276R (Revised). The Norton jet block should have a flat at the back with two small holes for the pilot air feed whereas other makes have a large central airway and the 'gusset' on the carb throat is machined away to allow air into the drilling.

Unfortunately, Burlen / Amal don't manufacture 276 (non-R) parts and offer standardised 276s for the Nortons so you won't be able to buy a replacement jet block from them to use with your existing body (assuming it is the correct original). I hassle Amals at least once a year but they have no plans to re-manufacture.

The Norton jet blocks are not easy to find. I've just recently bought one and had it sent over from Australia. I believe that Martyn Bratby can modify the other type so it might be worth having a word with him.

Duncan, you can tell that the jet block has been botched as it has been filed on the other side to give clearance for the tickover / slide adjusting screw. They were originally machined on one side only. There is no excuse for that sort of sloppy modification. Even if it was done years ago, you should have been advised that the part was not lsuitable for your body.

I'd need to see the bellmouth side of the jet block to tell if it's from a Norton carb. What is the number on your carb body as well ? 276/011 or 276/1BE ?

Duncan, I've been down the carburation desperation route too. There is quite a lengthy thread on the WD M20 forum which I put pictures of the various parts on. You should be able to see the mixing chamber and jet block variations.

http://pub37.bravenet.com/forum/static/show.php?usernum=3155626639&frmid=16&msgid=1224504&cmd=show

The clamp fitting was pretty much a vintage way of doing things. I don' think that many others used them. If you can get hold of a right hand block then that will help. As you'll have read on the M20 forum, several Norton chaps have run 'R' blocks in Norton bodies and say that it works. I can't see how the pilot air gets down the side of the jet block, although it certainly would if you eased the inlet tract a little on the bottom edge and made the air inlet drilling visible.

You haven't got a lot to lose by attempting to modify the jet block but it is actually three parts soldered together so make sure you don't get it too hot if you decide to have a go.

Martyn Bratby is usually at Netley Marsh. Are you going ? ...I'm just assuming that you're in the UK.