The BSA A7-A10 Forum

Technical => Amal, Carburation => Topic started by: Greybeard on 26.04. 2019 10:09

Title: Non monoblock flame-out
Post by: Greybeard on 26.04. 2019 10:09
My bike has started to occasionally flame out, usually when I'm about to pull away from lights. Its embarrassing to be trying to find neutral so I can kick it over! I have the original non monoblock carb that apart from this has been fine. I put a new slide and needle in 6 years ago. Any thoughts?
Title: Re: Non monoblock flame-out
Post by: Swarfcut on 26.04. 2019 11:58
GB.. I would check the idle circuit, as it seems either reluctant to draw fuel as demand increases, or over choking at hot idle. As it has been standing for a while, a good chance that a  carb clean  and blow through of the jets would sort it, plus the addition of a cheap inline fuel filter. Back in the day we would put on a longer length of transparent fuel line, dipping down then up in a "U". Easy way to catch the bigger lumps of rust and sediment passing the (probably) non existent fuel tap gauze filters. After a while, when no more bits came from the tank we put it all back to normal. Easier to take off the long pipe and dump the crud, rather than taking off fuel taps and float chambers.


 Swarfy.
Title: Re: Non monoblock flame-out
Post by: Triton Thrasher on 26.04. 2019 16:40
Are the plugs being sooted up by a worn needle jet or too-rich idle?

Points clean and gapped?
Title: Re: Non monoblock flame-out
Post by: Greybeard on 26.04. 2019 22:45
Thanks guys.
Swarfy, I did clean out the carb and blew compressed air through every little orifice I could see during my recent reassembly. I'm pretty sure the petrol tank is OK. I lined it 6 years ago with POR15 and it still appears OK. I've never seen any crud in the float bowl.

Yes TT, I'll check the plugs and points. I'm using some new old stock Lodge plugs with four electrodes. I'll try a modern pair of plugs.
Title: Re: Non monoblock flame-out
Post by: ironhead on 27.04. 2019 10:03
G'day Greybeard. Might be a silly question but have you got a heat insulator between carb & head? Fuel could be vaporising when idling & engine hot.
Title: Re: Non monoblock flame-out
Post by: Greybeard on 27.04. 2019 20:19
G'day Greybeard. Might be a silly question but have you got a heat insulator between carb & head? Fuel could be vaporising when idling & engine hot.
Hi Mr Ironhead,
I've just refitted the carb and put the thick, (3mm?) gasket between the head and the drip tray.

I'd only gone round the block when the engine conked out so it's not an overheating thing.
Title: Re: Non monoblock flame-out
Post by: muskrat on 27.04. 2019 21:19
G'day GB.
Have you tried richening the pilot screw 1/4 to 1/2 turn?

Ironhead, there's no such thing as a silly  *????*
Cheers
Title: Re: Non monoblock flame-out
Post by: Greybeard on 27.04. 2019 21:44
Have you tried richening the pilot screw 1/4 to 1/2 turn?

I was hoping that may be the answer