Hitchcocks Forum

I recently bought a 1948 Royal Enfield 350 Model G in great shape. However I have a persistent problem with the carb that I need to fix so that I do not blow up....

The carb is a bronze Amal 276 (original?).

The carb drips fuel out of the air adjustment screw. I have looked at the parts blowup and cannot see that any part is missing that might slow the flow.

The drip is slow enough that it will probably blow away behind me when riding, or possibly the vacuum will suck the fuel back in when the engine is running. But I am worried that if it drips onto the hot engine when parked after riding it will ignite!

Is this a "normal" condition for this carb that cannot be solved, or does someone know of a solution?

Thanks

Don`t know your bike model or the carb but it sounds like the fuel level is too high in the float chamber and should not touch the air (mixture) screw,the float may not be floating (hole) or the needle valve not shutting the fuel off at a certain level.
I would say it`s the needle valve and seat not sealing.

I have these carbs on several of my bikes and they are a s*d for leaking. As Jaffa says, it's probably the float needle sealing surface that's doing it but the seat can easily be disrupted by fine rust or grit in the fuel supply, try an in line filter if you can. The seat is very small so if you grind it in again use only the very gentlest polish or you'll ruin the seat. The good news is that new float chambers are available from our Hosts or direct from Amal UK. The bronze body is not original and sounds pre-war, post war ones were made of Mazak, a kind of alloy also used on Land Rover bodies as Birmabrite. Your bronze carb is probably worth more on ebay than a brand new one! Lastly, I'm puzzled you say fuel is coming out of the air adjustment screw, this could be the flooding but even so the screw should be a good fit (or it'll let air in, right?) or it'll spoil tickover.
REgards, Mark

Mark and Jaffa 90,

Thanks for the feedback. Yes, it seems logical that it must be flooding, and that I should probably work on the float and needle valve.

As the float chamber is pretty dinged up, buying a new one sounds like a good suggestion, and possibly even selling the carb and replacing it with the one that should be there. I was having trouble with the tickover which is why I rebuilt the carburettor recently. I had not occurred to me that the air adjustment screw not being (fuel) and air tight would be the cause of the bad tickover, but it makes sense.

Perhaps I can get enough for the bronze carb to replace the entire carburettor and chamber!

Thanks
Mark

beware!! my mates wdco caught fire twice with this type of carb so relutantly he fitted a monoblock & spacer from our host

Don't worry, sort the dripping carb and you'll be fine. If you have any worries, Bullets and some other models were fitted with a drip shield (I have one on my 1953 500 Bullet,) which will direct any spillage away from the magneto. This shield has almost always got lost over the years which might explain subsequent problems. Over 25 years with these carbs and I've never had a fire problem, but lost quite a bit of fuel!
REgards, Mark

Mark M, Adding a drip shield sounds a bit like putting those leather covers over the horns of a bull in the bull running. It might not actually kill you, just toss you over its head!
Having said that, do you have a part number???

Or even a photo so that I can fashion one?
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Hello CALIFORNIA model G ------ I don't want to sound like an advert for the "Nanny State" but carbs. are not meant to leak---period !! Those pre-Monoblock types -, especially very OLD ones, are notorious for their poor sealing qualities. And you've got a BRONZE one ??( Do you know what the market price of Bronze is just now ??). Ye gods man, it's got to be worth it NOT to fit it but sell it on the Vintage Bike Market and buy a brand new 276 from the manufacturers. If you do a quick Google for images you'll see that a Bronze one was not OE at the time, so yours would look wrong anyway apart from being tempting for any thief etc. PLUS---if you do have any probs. with a new one then it's up to the manufacturer to sort it for you !! ---IMHO as they say.

Alan R,
Did I sound like I needed to be brought back to my senses! OK, you and my wife are in complete agreement and I will be selling this leaky bronze carb, and the float chamber so that I can start with fresh (safe?)working gear.
Perhaps the problem is that I am working in the frame of mind I had 40 years ago when playing with these old bikes on a farm in the UK, instead of having got older and wiser. And yes, I did set a BSA on fire back then!