cutting out

[derek taylor]

just been for a run on the flash not been far since i got it but today put about 60mls on her,
came across a problem when i came to overtake wound throttle back, after half throttle she starts to cut out.
jets
pilot-25
needle-106
main-250
needle clip 2nd from top.

[Topdad]

Hi Derek, have you checked the carb for muck,check carb filter ,float bowl and then clean out the needle jet holder . If there is muck check the flow from the taps and if restricted or dirty check the tap gauges for crud. someone far more knowledgeable than will be able to help if it's not. Best of luck ,BobH

[derek taylor]

carb is clean and there is good flow

[Topdad]

What colour are the plugs Derek.

[Triton Thrasher]

If closing the plug gaps to 5 thou makes the symptoms better, it's an ignition problem.

Could also be water in the carburettor.

[derek taylor]

just had a look both plugs black.
bike will run ok if you wind the throttle up slowly

[chicago]

Too rich ?.

[BSA_54A10]

Sounds exactly like what happens when the main jet falls out or the needle gets stuck too high in the slide.
Up to around 2/3 throttle you are running on the tapper.
over that and you are on the parallel section of the needle.

[Triton Thrasher]

Up to around 2/3 throttle you are running on the tapper.
over that and you are on the parallel section of the needle.

No, fuel metering is gradually passed from the needle taper, to the main jet, above about 2/3 throttle.

The parallel part of the needle, in the needle jet, controls mixture at smaller throttle openings.

[derek taylor]

sussed it what a git you lot will fall about laughing,  bah did the last 60mls with choke on.

[Triton Thrasher]

Not your fault when the choke puts itself on.

[derek taylor]

ah its me just not used to it yet