Amal mk 1 settings (BSA C15)

[pierre66]

Hi, I have a 1961 BSA C15 with an Amal MK1 carb. The bike runs ok but you have to be very gentle when you open the throttle from tickover or it will stall and it is a bit lumpy on 1/4 throttle.

The carb is a 622.

3 1/2 slide.

needle on middle groove.

110 main jet.

105 needle jet.

Pilot air screw about 3/4 turns out.

Pilot bush fitted, I believe this is a 25.

The plug is black, not wet and never fouls (touch wood)

Will be grateful for any advice or opinions.

Cheers.

[b40rt]

Are you using a slow action throttle ?

What sort of air filter are you using, ie is it to restrictive ?

If you were in the UK Surrey Cycles can help

http://www.surreycycles.com/carb_01.htm

Edited April 15, 2011 by B40RT

[woody]

Your carb settings are the same as mine, I've pretty well cured the dreaded cough stall on mine by moving the carb further back using two tefnol spacers (20mm each I think). It won't stop it completely but I can open the throttle pretty quickly without problem and have to be pretty viscious on the throttle now to make it miss.

Not saying it will work on yours but worked for me. Found out by accident as I was trying to make the power delivery off tickover as soft as possible by moving the carb back and this turned out to be a side affect if you like.

Mine is standard road type engine (distributor model) with standard head/valves/cam, only mod is a 650 Triumph piston.

You can get the spacers from here if required

http://www.hitchcocksmotorcycles.com/amal-carburettors-miscellaneous

Just had my carb apart to clean it for tomorrow's PJ1 round and noticed I'd forgotten to mention one other thing. My carb has a 35 pilot jet fitted. The airway behind the pilot/air screw has been drilled out in order to allow a bigger pilot. Not sure what is involved in doing this as I didn't do it so can't offer any advice on this.

Edited April 16, 2011 by Woody

[pierre66]

Thanks for the replies.

Are you using a slow action throttle ?

What sort of air filter are you using, ie is it to restrictive ?

Yes, its the white throttle tube and its a conical air filter same as this:

http://www.trialsbits.co.uk/product_info.php?cPath=34_35&products_id=28

Always blow it out after every trial. Tried running it in the garage without air filter and its still lumpy at 1/4 throttle.

Thanks for verifying those carb settings Woody, at least I know they are something like, mines a standard dizzy engine with electrex electronic ignition.

I have a teflon spacer, its only about 6mm though, could maybe go to 10mm but not a lot of room between carb and oil tank.

If I`m honest its always been lumpy at 1/4 throttle and the "cough/stall" coming off tickover, on the clubman route I`ve ridden round it but now I`m trying the expert route its harder to ride round this small problem.

Thanks again guys.

[b40rt]

Just to confuse the issue,I found your air filter made my B40 run weak, and went for one like :-

lightly oiled with proper air filter oil.

(Also easier to get into a tight space)

Edited April 16, 2011 by B40RT

[bashplate]

Just to confuse the issue,I found your air filter made my B40 run weak, and went for one like :-

lightly oiled with proper air filter oil.

(Also easier to get into a tight space)

hi, i'm using a k&n type filter on my honda, and was looking at these foam type ones....do you recon they're better?

as regards the C15 running lumpy at 1/4 throttle, this sounds like its rich....is the float set a bit too high, or do you need a bigger cut away on the slide perhaps?

as a no cost try it solution ,try dropping the needle, and also the pilot air screw should be 1 1/2 turns out....this would let more air in the pilot mix which might help the 1/4 throttle transition.

Edited April 17, 2011 by bashplate

[b40rt]

hi, i'm using a k&n type filter on my honda, and was looking at these foam type ones....do you recon they're better?

Don't know if they are better,but I like a bit of oil to trap the crap, and I think they are easier to clean, IMO