Yes it is actually 3 pieces the top part, bottom part and the little circular bit in the centre of the bottom part. The black suggests that it has been loose for some time. They are fiddly to put back together as you only need a thin amount of solder and have to be perfectly vertical otherwise the slide will jam. Also make sure you can poke a wire through the small hole otherwise you will have problems with it idling. I used a small gas gun to do it. Burlen the manufacturers of Amal carburetter do not sell the jetblock as an individual item. I know Martyn Bratby was talking about manufacturing them but don\'t know if he did.
Thank you very much. I will take a shot of putting it back together. I have several butane, propane and Mapp gas flame throwers. I already fitted a wire through the hole. Flux it really good, clamp it together and apply the fire.
The rest of the bike is coming together. Waiting on carb gaskets, a few nuts and bolts and she should for the first kick in years.
I found paperwork, receipts showing new brakes, dyno rebuild, tires, clutch and plate and more. Very few miles were put on it after that rebuild.
I set the jet body up on a level table. Ran a stainless wire through the hole. I fluxed to up, added a little solder to the shorter bit. Then I dropped the longer bit on to the lower bit and heated the blocks. Solder was sucked into the joint. I put a weight on it until the solder set. Cleaned up all the excess flus, removed the ire. Or should say it just fell out. All passageways are clear. The unit went back into the aluminum bit with a little heat and a couple of taps alll back together. Easy job. Of course the proof will be working on a running bike. For now it will stay a spare.
Thanks for the advice.