Warm starting problem

[Pastie]

Apologies if this has been covered before. I have a 1953 16 MS with the original carb, float chamber and float, and mag. The bike runs really well and starts from cold usually first or second kick. She also starts when hot really well, but I am finding it really hard to start when warm, if the bike has been stopped for about 30 minutes or more, but is not completely cold.

I know old bikes all have their foibles, so I have tried every combination of different positions for the advance/ retard lever, different positions for the choke lever and I have tried tickling & not tickling as well as turning off the fuel tap when stopped, and leaving it in the 'on' position. I have also tested with an in-line spark indicator, and the spark is good when the bike is cold, warm and hot, so I think the problem probably has to be fuel related? Someone recently suggested fitting an Amal 'stay-up' float.

Has anyone experienced the same problem and hit on a solution? many thanks in advance for thinking about this.

Pastie

[spookefoote1956]

Magneto needs looking at. If you're lucky it'll be the condenser. Hope you're lucky!

[Mick D]

Hi Pastie

I agree with you, it sounds like a fuel / technique issue.

I find my bikes tend to start best from cold with a tickle and the choke. When warm, I give the barest touch of tickle and no choke. From hot no tickle or choke.

Regards Mick

[Pastie]

Thanks for the quick replies Mick D and Spookefoote.

I'll try a very slight tickle and no choke first and see if that is any better.

Failing that, it sounds like I need to look at the mag/ condenser. If the magneto is failing, would the spark still look good when I do the in-line spark test?

Thanks
Pastie

[Mick D]

Hi

Mag faults usually get worse as heat increases - if it starts well hot and cold it's unlikely to be the mag. Also if the mag was breaking down due to heat you would experience erratic ignition when hot, not just starting issues.

With the symptoms you describe, the mag would not be high on my list of suspects.

Regards Mick

[robcurrie]

Have you got the insulating spacer between the head and carb?
Rob C

[dave16mct]

Same as the mag, it'd be worse the hotter it got. How original is the bike? I find monoblocs are a lot less trouble!
Dave.

[Stan Palmer]

Might be a naive answer, but this sounds like the first problem I noted with ethanol fuel. Taking the pilot jet out and thoroughly cleaning it was the initial solution, I finally solved it by turning the petrol off when the engine was still running and letting it run dry. Once the jet is really clean you only need to do that if you are not using it for a week or two.
Stan

[Pastie]

Just wanted to say thanks for all your help with this. I've had several run-outs since posting about the problem and I found that trying the 'barely a carb tickle and no choke' method, coupled with changing my kick start technique (I stand over the bike now, rather than trying to kick over from the side of the bike,) seems to have cured the problem with warm starting. Thanks. Pastie