B31 Float Chamber Fuel Height please? - fuel starvation causing stalling

[Fraz]

1954 B31 Plunger with stock Carb.

Randomly, the bike will stall (even whilst riding) and not restart.

I've narrowed the problem down to fuel starvation - as the engine starts to die, tickling the Carb brings it back to life.

Carb has just been totally stripped and cleaned and the only thing I can think of would be incorrect float height (although the issue is random and sometimes it will run OK for miles and other times just for 50 yards before dieing again.

Could anyone please tell me the correct fuel height in the float chamber and how to adjust the float height?

Many thanks

[DAVE BRADY]

Hi,

This may seem a bit basic but is the breather hole in the fuel cap clear.  Even if you can blow through it it may still be obstructed.  My wife's A10 started to behave in a similar way and I suspected carb. etc.
When I checked the filler cap it looked fine but when put back on the tank I could see some debris inside that partially obstructed the hole.  After trying to remove it and failing I fitted a new cap.  Blowing through the old and the new demonstrated how much clearer the new cap is.  The bike behaved itself after that.

Dave.

[Fraz]

Thanks.
I've don't the "blow through test" as you did but I'll try it tomorrow with no filler cap in place and see what happens.

The strange thing is that it ran for 15 miles, coffee break and 15 miles back, with absolutely zero problems.
The following day, it ran 10 miles perfectly but on the way back, started acting up.

I'm struggling to find any sense with it.

Fitted new plug, cap & HT lead too, in case it was electrical.

[bikerbob]

To check the correct fuel height in the chamber, if you look at the float chamber cover it should have a casting pimple just below the letter M in the AMAL name this is the correct height for the fuel in the float chamber. Some covers do not have this pimple so use the bottom of the letters MA as the correct level. Now to check this there are 2 ways to do this you could make clear perspex cover and put it over the original cover put a dot with a felt tip pen at the correct level then remove the existing cover and fit the perspex one and turn on the petrol to check the level. this cover does not have to be anything fancy or even round so long as it is flat and has the correct holes in it in the right positions. the other method is to remove the  pilot jet cover and fit a bit of clear tubing that is a push fit over the pilot jet  then bend the tube up in front of the float cover and turn on the petrol which will fill the tube up to a level which may to hiigh, low or correct. to adjust the fuel height beneath the fitting that holds the fuel filter and banjo there may be a washer if the fuel level is to high then remove the washer if to low then add a washer. this may sound a bit complicated but is the correct way to check the fuel level hgeight in the float bowl.  If you put this number into ebay it will give you an idea about my explanation 204464547466 it shows the perspex cover and washers for setting the correct height.

[Fraz]

Fantastic, thank you.

The float height / fuel height is spot on so my problem kids elsewhere.
I've been told it could be the Magneto failing?