Hi all.
My 1953 B31 is fitted with a 276 pre monobloc carb which is continually leaking. I have rebuilt it and on the bench it doesn't leak. Then back on the bike, sometimes it leaks, sometimes it doesn't.
I've got to the point were I am sick of taking the damn thing on and off the bike and replacing it with a monobloc carb like the one on my B33, which never gives me any trouble.
Can anyone suggest the appropriate carb I can use to replace the one on the bike.
I thank you in advance for any help.
Malc
I think you would be looking at a 1" choke 376 Monobloc. If you look on the AMAL web site, they show the 1955+ B31 fitted with this carb.
Thanks Spaceman. I'll give it a look.
Where is your 276 leaking from?
From Amal, this is what you need : https://amalcarb.co.uk/carbspec/carburettor/spares/id/4659/ (https://amalcarb.co.uk/carbspec/carburettor/spares/id/4659/)
I would just fix the leak on the one you've got. You can get all the parts from Amal. I've had three B31's with 276's without any trouble. I put a monobloc on my last B31 to see if there was any difference and there wasn't.
From a engine performance or pure carburation point of view, I don't think there is any real difference between the 276 and its 376 Monobloc replacement. If you go for a new 376, it's going to perform a lot better than a possibly worn out 276 and will also not have a tendency to leak petrol quite so much!
Hi. Thank you to everyone that have replied.
The carb is leaking from the area where the brass nut hold the jet block in position.
I have replaced all serviceable parts using Amal overhaul kit, this includes the float, float needle and all gaskets.
I'll attach a picture of where it leaks if my rubbish tech skills can stretch to that.
Once again, thanks to all that have taken the time to help.
Malc.
Have you got the thick fibre washer in the bottom cap? It then needs to be done up fairly tight.
There's also a hole in those threads that is there to let excess fuel flow out, indeed when you tickle it it should come out there and not the top.
The usual reason it flows out of there is fuel level in the float chamber is too high.
Have you changed the original float for a new plastic one? If so the needle has 2 grooves for the clip that holds the float, if you look carefully you can see they are marked C & P get it in the wrong one and it will flood!