My Chummy will start happily when cold and idle nicely, but if I turn it off and try to start it when its hot, it won't start even after being tickled and trying to start with the choke.

Its on 12v so the starter turns it over nice and fast but no joy.

I believe the timing is correct, its running with a BLIC mag and the revs increase a little and stop as you advance it on the hand controls.

It will however bump start with a good hill in second gear, run badly for a while and then fine again.

Any ideas on how to fix this would be greatly appreciated as ever!

Will

Location: Bishops Cleeve

Will, has this started happening recently in the hot weather? it could be fuel vapourisation. If it starts ok after a cooling off period , it would suggest that the petrol has boiled in the carb. When it happens,can you cool the carb with a wet rag wrapped around it to aid cooling,or better still a can of freezing spray used to freeze pipes in plumbing. If these measures help the answer is to stop the carb from getting too hot. Maybe a heat shield made from aluminium sheet and/or a bakelite insulating spacer between the carb and manifold to stop heat transfer. Choke use will only add to an already over-rich mixture. Of course there may be another cause but I would try these first.

Location: Piddle Valley

Thank you for the suggestions, I left it for a good half hour yesterday to cool down to see if it would start, but still no joy unfortunately. The engine was still hot, but the carb can't have been hot enough to cause vaporisation at that point surely? maybe it was!

Its a newly built engine that I've yet to have running as it should do.

Location: Bishops Cleeve

A faulty coil in the magneto will give those symptoms.

I would say that it is almost certainly the mag, could you try another that is known to be good.
It might be the condenser in the mag, you could try another externally.
Hope that is helpful !

Location: The Centre of the Universe

I have a spare mag so will give that a go this evening. This new engine is being a bit of a bugger, I may just plop the old one back in now I've fixed it.

Thanks for the suggestions!

Location: Bishops Cleeve

Will - I'd support the suggestion above - if an engine won't re-start after getting overheated, you'll have no success using the choke - I'd suggest it will only make the problem worse. Cheers, Bill

Location: Euroa, Australia