Okay, I can cold start fine, but hot starts results in the battery acting like it's flat. I slap on my starter unit (sealed cell battery with jumper-like leads, you know the sort of thing; Supercheap sell 'em), and it starts right up.

Is it the battery, or something else? The fact that it starts okay (most times) from cold makes me wonder.

Incidentally, it's my Commer van, not my mini but the overall system is the same so I figure the principles are the same too

I'd check all the battery cable connections for starters, and the engine/chassis ground cable.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Batteries tend to die when the weather gets chilly and seeing how the chill has just started I would normally guess that the battery is on its way out. (Just wait and see how many threads we get about hard starting in the next few weeks.) But your problem sound a bit like a starter problem. Check the battery power and make sure everything is clean and tight.

this might sound wierd, but it could be because the timing is too far advanced and the spark is igniting the start-up mixture too early and the combustion is stopping the piston half way up the compression stroke

when the engine is hot the compression is a bit higher because everything has expanded, maybe it starts OK when cold because of blowby on the pistons, but more compression when hot and it can't start it

of course, a crook battery would be affected more than a good one - so my theory, and a crook battery theory might go hand-in-hand - crap battery starts it fine when cold, but not when hot

ummmmmm

so I agree with them - crook battery, good timing, retard the timing will let it start but the timing will be crap, so replace the battery

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did I tell you that I won a trophy?

your theory is good Simon. I have similar issues now and then, and I do tend to up my timing more than I should.

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Website: www.justanothermini.com

yeah, my K used to do it sometimes, my mate said "it's compressing against itself" - didn't ping though

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did I tell you that I won a trophy?

The brickworx truck did it when it ran hot... Never started again