BSA Owners' Club Forum

The BSA Workshop => Singles => Topic started by: BANHAM on 31 March, 2017, 20:18:46

Title: B25 Difficult Starting
Post by: BANHAM on 31 March, 2017, 20:18:46
I have a 1969 B25, which I have just finished a nut and bolt restoration. When running it performs well, no flat spots, never misses a beat and accelerates well. I've just completed 350 miles and its last run was over 150 miles. I am running with a Boyer mk4 electronic system and a new Mk1 Concentric carb.

 BUT from cold the only way it will start is zero throttle, flood carb, find TDS on the kickstart and kick.  If you are lucky after the third or fourth kick it will start and when the rev's pick up you can open the throttle, otherwise opening the throttle will stop the engine.

When its warm , starting is in the lap of the gods, sometimes with throttle, sometimes without.


Title: Re: B25 Difficult Starting
Post by: MICKREEVES on 21 April, 2017, 18:51:13
I have just discovered a way of starting my C15 SS, from cold, First kick every time.
with the throttle stop set for a good idle when cold, I dont choke or tickle, or touch the throttle.
As it warms up, the stop has to be turn back lower for hot tickover.
To find the starting setting again, I have soldered a piece of piano wire into the throttle stop screw,
so that I can easily see or feel exactly where it is.
Title: Re: B25 Difficult Starting
Post by: TIGER on 23 April, 2017, 06:04:01
       I have some difficulty starting my. C15SS FROM COLD.
       I noticed some pictures from Julian show an additional lever on the handlebars.
       Is this a choke which could help !
        I have a Amal 375 (I think standard fitting)
        Where can I buy this fitting ?
Title: Re: B25 Difficult Starting
Post by: JulianS on 23 April, 2017, 10:21:14
You will need an air slide, spring and guide for the carb and a cable and handlebar lever.

All the carb bits can be obtained from Amal

The lever and cable from your favourite dealer.

These bikes should start easily with or without the choke - tickle the carb switch on ignition slightly open throttle and kick. Make sure the carb throttle slide is raised enough on the throttle stop to allow a little air through otherwise no petrol will reach the engine.
Title: Re: B25 Difficult Starting
Post by: BANHAM on 23 April, 2017, 16:23:04
Problem solved, I've fitted the next size pilot jet and she starts first kick with throttle. The nice thing about a Concentric MK1 Premier Carb, they are easy to change. Many thanks for your help.