Can you help

[Bikergrandad]

  Hi to all. I have a BSA B31 1954  I have a problem, it starts straight away, the tick over is very good.
  Compression is very good, carburettor been cleaned lots of times.
   Magnetos been rebuilt very good spark, I have checked the cogs on the timing they are ok.
   New spark plug. High tension lead, cleaned the tank out, a filters ok.
    But when I go for a ride and open the throttle it starts to die like no petrol.
     But I have checked all over and over.  any ideas thank you  Bob.
   
     
               

[bsa-bill]

sounds like carburettor - jetting maybe
another suspect might be your fuel tank cap, check that the breather hole is clear

[muskrat]

Ditto fuel cap. Do you get further with a half full tank than a full tank?
Cheers

[duTch]

 

  with a half full tank than a full tank?

 ... Or a half empty tank. ..?

[muskrat]

With a full tank it will happen sooner than a half full one due to the amount of air in there.
Cheers

[duTch]

 One day I'll stop being a complete bastard.....

[Johnny J]

Hey duTch, riding old motorcycles you need to have a "half full" state of mind. :-)

[edboy]

bikergrandad, when it dies on you next time could you turn off the petrol and take off and check the float bowl for the correct fuel level? it sounds like fuel starvation.

[Triton Thrasher]

With a full tank it will happen sooner than a half full one due to the amount of air in there.
Cheers

Just clear it, and there's no need to worry.

[Triton Thrasher]

If the tank breather is clear, Take the jet cover off the bottom of the carburettor  (look inside it for water) and drain petrol into a jar, with the tap open. Should be more than a dribble. More like 300 ml per minute.

Check the main jet for blockage.

[bikerbob]

You could also check the level of petrol in the float bowl. A quick way of doing it is to take the cover off the pilot jet put a length of suitable tubing over the pilot jet and bring the tubing up in front of the float bowl. If you look at the word AMAL on the float bowl there should be a cast pimple between the M and the A this is your float bowl level . Turn on the petrol and it should fill the tubing up to the level of the pimple if significantly below that level then when you open the throttle you could be taking more petrol out than is going in. I am assuming that you have a 376 mono bloc carb fitted.

[Andreas Larsen]

Not sure if it could be the problem, but I experienced that my A10 would die on me after riding say 10 miles or so, or if I gave it a little more throttle - the problem was the fuel taps, the rubber inside would swell up, probably due to ethanol in the modern fuels, and the engine would starve as the carb ran out of petrol..

Does it get better if you leave it standing for a few minutes and then the same thing happens again after a few miles?


Andreas

[nimrod650]

try lifting needle a notch or two

[KiwiGF]

hi bikergrandad, has it got a monobloc? I had a problem with the tickler being blocked on mine it doubles as a breather, caused the engine to die after running a while. It only takes a couple of mins to check it.

I eventually found the problem after using cling film instead of fitting the bowl side cover, so I could see the petrol entering and float bowl and valve working, or not in my case as the pressure built up as petrol entered and the float did not reach full level unless left not running for a few minutes.

[Bikergrandad]

 I to all. Thank you all.  When I have the bike on the stand, and open the throttle it don't die.
     Only when I go for a ride up the road no acceleration.
         I will let you know how the bike goes when I go back working on it.  Bob