I just made one for a diesel engine. Aluminium kitchen foil is too thin to seal, but two layers works fine. Disposable aluminium oven trays are great but I didn't have any. Then it hit me the foil pouch that I had just got my new #11 blade out of was perfect.

Or an adult fizzy drink can will work great as well.

Take the cylinder liner out of the engine and carefully hold the foil over the top end. Carefully cut around the inside with a scalpel or sharp modelling knife. Press around the outside edge with your fingers to mark the foil, then cut out with sharp scissors. You may need to make 3 or 4 before you get a nice one.


Are you sure it's missing? Sometimes they hide in the cylinder head and you have to carefully work them out with a pin. Don't slip and scratch it or bend it or you will need a new one anyway.

You need to be carefull about what thickness you end up using, too thin can let the piston hit the head, or can lead to detonation, overheating, blown plugs and engine damage. Too thick can lead to low power and the plug cooling off and the engine stopping. It all depends on how much nitro you are running, what propeller load, how much cooling the engine gets, etc. But if your engine runs fine now you should be fine with any of the aluminium thicknesses mentioned so far.

Daved H