I was getting these cylinders for replacements when I was getting parts.

The first ones I took to a machine shop and had them milled for the cm6 plug to work, Sent Kevin (JC engine) a email about it but was told they were ok and to just use them.

Was costing me a good bit of change ($) to do that so I started changing the plug caps to a 5/8” hex cap and using a NGK CMR7A spark plug. This let the electrodes to protrude into the combustion chamber.

I don’t think nobody knows the he** I went through repairing JC engines.

Milton