You turn off your car but it turns over once more after the key has been turned off? What do I need to adjust?

It's called run on. Has something to do with the carby being too lean or rich, i believe.

or your engine being coked up

Run-on , pre-ignition several other names , basically it means for some reason the fuel/air mix is igniting under pressure in the engine even without the plug sparking . Has it always done it or only just started lately ?

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have been playing with the twin carb tuning, so is that the likely cause

If mooman doesn't mind me jumping in, the BOC's always done this on and off (i posted about it just after i joined) and it hasn't chanhged.

It's usually a sign that my oil's a little low.

My car used to run on all the time until it was properly tuned. It's often a combination of things:

* Too rich mixture
* .. left for too long, causing excessive carbon buildup in the combustion chambers. This glows and stays hot and ignites the air/fuel mixture after the ignition is switched off.
* Timing too far advanced, causing higher than normal engine temperatures.
* Compression ratio too high for the octane fuel you're using, allowing the fuel to detonate under compression (like a diesel).

Run-on is a sign of bad things going on in your engine and you need to do something about that. In the interim, I always used to control the run-on using the clutch in gear -- not good, but better than letting the engine fire uncontrollably and potentially blowing a hole in a piston/valve.

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Simon

The adventures of an owner builder in the Tallarook Ranges