Today I was sitting at the lights with my mini idling and it started to miss I wasn't far from home so I drove the next few hundred metres in first gear very slowly, upon getting home I removed the plugs to check them out and was shocked to find number one plug in this state.




What would cause this to happen at idle?

Looks like something is floating around in the combustion chamber.....a bit of valve, piston or ring? Looks like the thread has been hit by something too!

I forgot to mention the engine done this approximately 6 months ago on one and two, upon discovery I removed the head but could not find any object or damage inside the chamber it seems very odd to me, I will be removing the head to check again though.

I would also say looks like something has been in there that doesn't compress very easily.

something may have been sucked in and then passed through into the exhaust. I had a piece of carby slide break off and do the same to a plug on my bike !

You could use 'short reach' plugs!!! They lower compression and will also prevent this from happening again.

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Sh*t that don't look to good it may have passed through into the exhaust by now.

It must be of some concern that this same event occurred recently?
like norton mentioned, have you any missing pieces from the intake side?
Limit valve still in one piece?

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It's easy once you know how.

Its amazing what you find in engines sometimes.
I had a hilux that stalled one day. Popped the bonnet and noticed the aircleaner was loose and the centre stud on the carby was missing. Found the stud stuck in number 3 inlet valve. A $50 head gasket and 3 hours later it was running again.

Still have both the screws on the carb butterfly? They're deformed from the factory so they don't come out but if someone's put a normal screw in it could have fallen out and been sucked in. Personally I would pull the head. You'd have to be very lucky for it to have missed the valves on the way through.

If u have double valve springs make sure the inner spring isn't broken and losing peices could explain y it's done it twice mayb

that is interesting, can this still happen with single valve springs?

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It's easy once you know how.

Certainly important when you have coil bind from too great a lift for the springs, but there's not really a path into the intake from the rocker cover.

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SooperDooperMiniCooperExpertEngineering

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Didn't think of that now lol my bad

Might pay to borrow a bore scope and have a look in the cylinder?