Hi, i have a b31 (400cc) with an AMAL 276 carburetor it runs very well , but starting it has not been easy often with a push off.
I am just checking every thing over at the moment, looking at the jet block it has 51 stamped on the top and 30t on the bottom is this the correct one thanks

The air slide is 6/4

Thanks

Throttle slide (note, not air,) 6/4 sounds rather weak to me, l'd think 6/3 and 1/2 or possibly 6/3.
REgards, Mark

Steve the Amal book quotes for B31 1946-54 1" bore - 150 main jet - needle position 3 - 6/4 slide.

Maybe a strip and clean might help with special attention to the tiny hole in the bore behind the slide. It needs pocking out with fine wire after you've removed the jet block (also clean the corresponding drilling in the jet block)......Or maybe your problem is the mag? Ron

email (option): ronpier@talk21.com

I'd second Ron's comments. I have rebuilt several of these carbs and they can be a pig to get running correctly. The original settings always seem quite weak to me (hence my comments) and I have had better results with less throttle slide cutaway which is why I suggested it. Data on these carbs is a bit thin, my research suggests 51 is a part number and 30T is the identification of the pilot bore drilling. There is no detachable pilot jet, it's the drilling in the jet block that does this function. There was also a 25T block but any original parts are hard to find and worn when you do! On the subject of the jet block, be careful how much force you use when tapping it out of the carb body, the thin brass can easily distort and then you're really in trouble. I use a scrap needle jet screwed in the bottom of the jet block to act as a puller while tapping on the top with a piece of wood. Jet blocks are often very tight fitting (although you may be lucky,) and I've found heating them in a pan of boiling water helps extract the block.
REgards, Mark

OK all jet blocks have 30T stamped on the base. your original carb was a 1 inch so should be marked on the top of the jetblock 45, yours is marked 51 so that denotes 1 and 1/16 jet block. B31 had carbs marked on the right top of the mounting flange 276AW/1BB for 1946 to 1948 and 276DR/1AT for 1949 to 1954. Is your bowl marked on the arm either 1BB or 1AT I suspect you have a 1 and 1/16 inch carb fitted and possibly the wrong angled bowl? These carbies are pretty simple so if you have fuel and spark it should at least go close to firing or backfire on each starting attempt. I have a mate here in Australia who reconditions carbies and has a sign in his shed that states "90 per cent of your carby problems are not the carby" as it is often worn valve guides or magneto problems or timing out one tooth. In your case as it runs good once started I like Ron suspect the magneto.

Thanks for the advice and i will look into the magneto as well.
I thought mags only gave problems while hot. That,s how much i know :)

If it is the mag, should I fit the bright spark easy cap condenser while its apart or just go with what ever the mag person recommends
thanks.

I've never used the Bright Spark thing. The mag guy that I've used for years has told me on numerous occasions, that I won't be bringing one of his refurbed mags back in my lifetime. Ron

email (option): ronpier@talk21.com

I had a look at the Bright Spark condenser website as I think I may have a condenser issue. For an MO1 it looks very difficult for an idiot like me.

When I get the mag refurbished, I think I will go for it as an external condenser seems very logical.

Ron

Where do you send your mags to for a refurb?

Regards

Pat

email (option): sacombsashtrees@hotmail.com

for well over 20 years I've used a guy in the New Forest who's hobby is collecting magnetos. All the mags in his collection have to be fully restored so he acquired all the equipment and taught himself to restore them years ago (and that is about every type of mag you can think of). He never advertises but is well known locally and also by tractor, aviation, car/motorcycle clubs all over. He's not quick! His queue is usually about 6-7 weeks. Email me if you want his contact details. Ron

email (option): ronpier@talk21.com

PS. Latest one for me was this rare and finicky 'Miller' unit which I acquired in a totally dismantled condition. Ron

email (option): ronpier@talk21.com