The BSA A7-A10 Forum

Technical (Descriptive Topic Titles - Stay on Topic) => Amal, Carburation, Fuel => Topic started by: derek taylor on 05.05. 2014 16:09

Title: cutting out
Post by: derek taylor on 05.05. 2014 16:09

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.

Title: Re: cutting out
Post by: Topdad on 05.05. 2014 16:38

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

Title: Re: cutting out
Post by: derek taylor on 05.05. 2014 16:44

carb is clean and there is good flow

Title: Re: cutting out
Post by: Topdad on 05.05. 2014 17:02

What colour are the plugs Derek.

Title: Re: cutting out
Post by: Triton Thrasher on 05.05. 2014 17:29

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

Could also be water in the carburettor.

Title: Re: cutting out
Post by: derek taylor on 05.05. 2014 18:01

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

Title: Re: cutting out
Post by: chicago on 05.05. 2014 22:11

Too rich ?.

Title: Re: cutting out
Post by: BSA_54A10 on 06.05. 2014 09:10

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.

Title: Re: cutting out
Post by: Triton Thrasher on 06.05. 2014 17:59

Quote from: BSA_54A10 on 06.05. 2014 09:10

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.

Title: Re: cutting out
Post by: derek taylor on 06.05. 2014 18:04

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

Title: Re: cutting out
Post by: Triton Thrasher on 06.05. 2014 18:18

Not your fault when the choke puts itself on.

Title: Re: cutting out
Post by: derek taylor on 06.05. 2014 18:30

ah its me just not used to it yet