BSA 1961 C15

[Colin Sherwood]

PLease Help ! I live in Devon (Exmouth nr Exeter) and trying to find someone local who can help me with my bike, I have enough knowledge to be dangerous ! it was bought as a Non runner about 12 months ago, and I have been slowly working on it, with my Dads help, but he passed away just recently, I replaced the Carb, as it had the wrong one previousley fitted, with a brand new Wassell, the bike starts up lovely, but when riding, it constantly pulls when you accelerate, like its mis-firing, I have tried tweaking the pilot, but no change, it seems to make a difference when I adjust the choke as I ride, but only for a little while, then it starts pulling again, very frustrating, as I would love to have a good ride out on her, I would be happy to pay for someone to check her over, and tweak as hopefully required?

[V500]

"Pulling"?

[rhyatt]

Carbs have a few sections of operation over the throttle range.
You've established the the beginning , starting bit is fine.
Have you or did you - before fitting it - check that the inner needles and jets were correct to specification in the C15 book ?
Check them and come back

[Colin Sherwood]

hi Thank you for the prompt reply its much appreciated, and as mentioned I no enough to be dangerous, I bought the Carb from Surrey Cycles, who deal with Amal and Wassell Carbs, before I picked it up, I gave him the bike details and he set it up for me so all I had to do was fit it ? which I did, apart from some advice I was given on the BSAOC Stand at THE Stafford show just recently, where the chap there suggested I screw the Pilot jet fully home then wind it back out 1 1/2 turns, which I did and it has not really made a difference, I was wondering if the timing could be out, which is why I was hoping to find a Local Eng to give her a check over, which would allow me to look on and learn a little bit more ?
what i don't want to do is mess about with it and make it much worse.

many thanks Colin.

[Colin Sherwood]

hi Thank you for your reply, when I say pulling, its as I accelerate away the bike is jerking away and will not run / ride steady.

[DAVE BRADY]

Hi,

Is there a choke fitted to the carb.?
Some C15s did not have them.  If there is one then the lever must be pulled to lift the choke off.
The choke will make starting easier but if left on or lowered then the engine will behave a bit like you have described.

Dave.

[Beesy]

80% of carb problems are electrical.

Are you on points ignition or electronic ignition?

If you sure you've checked everything on the carb try a new condenser and coil.

From my experience if the bike starts easily then generally the timing isn't too far off.

[Colin Sherwood]

Sorry for my late reply, driving all over the Country.
yes it has a Choke fitted in the carb,this was reconnected to the lever that turns back and forth as used on the handle bars, and that seems OK,

there was a Boyer Electronic Ignition fitted when I bought it, neither this or the Coil has been touched whilst I have had her, do you think a new coil or condenser would help ?

would anyone no of a Mechanic in this area I could get to check her over, so I can be sure everything is up to speed ?

[DAVE BRADY]

Hi,

Are you in the BSAOC?  There is a Tamar Valley group, members of which will almost certainly help.

Details in The Star or on the BSAOC website.

Dave.

[Beesy]

It won't have a condensor as it has electronic ignition.

I had similar symptoms. A spluttering on acceleration and at higher revs. Seemed like it was a fuel issue. After several days of cleaning and fiddling with the carb a new coil cured it.

Changing the coil isn't too difficult. It's only swapping wires over like for like. Pay attention to the + and - markings.

I'm not sure if your coil is under the seat or under the tank.

I'm a bit too far away in Bath to visit.

[Colin Sherwood]

thank you both, and yes I am a member, I will try a new coil which is under my seat, and keep my fingers crossed, otherwise I will try to contact the Tamar Group.
thank you both for the support.

[rhyatt]

Never spend money on randomly purchased parts.
Diagnose and understand and grow the empathy with your bike.
Does or does not a spark appear when kicking over with ignition on?
If no , then is the boyer trigger unit telling the boyer box to spark ?
Is there 12v etc etc

[V500]

Yes, repair by substitution is never a good way to fault-find if you're paying for the parts used.

[Tigerfeet]

Going back to Dave Brady's point, and your reply 'yes it has a Choke fitted in the carb,this was reconnected to the lever that turns back and forth as used on the handle bars, and that seems OK,'.

The BSA choke lever works in the opposite sense to bikes such as BMW's.  I'd suggest you take the rubber air inlet tube off the carburettor so that you can see (or feel) the position of the choke slide. With the throttle twist grip held wide open, and the choke lever set to 'off', the only obstruction in the carburettor should be the needle. Then look again with the choke lever in the opposite position.  Your symptoms are exactly those you would get if operating the choke in the reverse sense....

[rhyatt]

I'd suggest removing the nearside tool box cover , 2 screws , now remove the wire circlip holding the air filter gauze in place.
Now you can peep into the carb intake.
Thise rubber tubes are a b-----er to get back on .
This will enable you to understand the choke operation