confirmation needed, [or not]

[mini-me]

Ok I'm pretty sure I know the answer to this, but.......

On one of my 1930s bikes  has always been a sure fire one kick starter,  now after a run out it and a halt, ie for guiness and pie,  refuses to start unless I change its plug, doesn't need to be a new one,just another plug when it's first kick again.

I am suspecting condenser failure, but  in case anyone has any better ideas?  just before I take the mag off that is.

It was a brand new mag out the box 45 years ago....................

[Rex]

Certainly gives the impression of a failing mag, and the most common cause of a failing mag is a failing capacitor.
Nothing in the carb is going to give those particular symptoms.

[iansoady]

Apart from vaporisation? Changing the plug might just give it that extra bit of time to cool down. I had a 16H Norton many years ago that was plagued by this - made worse as it had the clamp mounted carb so no opportunity to fit an insulator.

But I agree that my prime suspect would be the capacitor. It may be worth trying one of the Brightspark type?

[mini-me]

thanks all,  I considered vapourisation, might try an insulation block, as it's only when hot but that could apply to capacitor as well  otherwise resigned to magneto o/h.

A bit pissed off as the mag is only 45yrs old, they don't make stuff to last anymore.

[R]

they don't make stuff to last anymore.

Thats quite true about foil condensors - they are already a failure waiting to happen, even  when newly made.

Its big business these days replacing them in stereos and old radios and TVs and all the electronic equipment that used them.
Having had one explode once when I switched on an old stereo amp, I can vouch that they are trouble waiting to happen !

If you see the size of the little jiggers in these brightspark units, you realise that technology has advanced somewhat over the years...
Spot the brightspark easycap capacitor here.


If changing the plug INSTANTLY fixes the problem, that sounds more like an overheated?/unhappy? plug though ?

[mini-me]

Thanks, some ideas there. I thinks I'll try an insulator block first. Been considering those new capacitors for a while, looks like time to bite the bullet, but I hate to interfere with something working well when its not dud.

[Rex]

I suppose when you say that changing the plug sorts it it depends how long it takes to change that plug.
If you whip out the old and screw in a new in under a minute then that's not linked to vaporisation as the heat won't have dissipated that quickly. If you let it cool down while having a cuppa then possibly.
Thing is, if the bike behaved OK before with no insulator then it's unlikely to affect it now.

[mini-me]

I agree Rex, but its got an iron head which gets quite hot, couple minutes to change the plug IF only if it utmost refuses to start, thing is, if I advance the ignition to check if there is life it won't even kick back, but will when plug changed. It don't like the muck we are sold as fuel for sure.
Anyway fitted an insulator, out for a run tomorrow to see.