It's a rod-actuated cylinder de-honing tool.

Blinker fluid reservoir cap?

Burnt suitcase wheel?

That pops out of the engine to let you know that it's time to change your oil.

Easy, tail pipe plug to make your bike zero emissions. Low quality ones melt after just a few miles.

Part of Sputnik.

Pocket ashtray

Muffler bearing

Molten slag from scrap metal recycling?

Lunch.

A coin purse?

Is that (or was that) a piston head?

Pre-chewed liquorice?

Expensive!