Ignition timing for long stroke polini 208

HI there,


I've got a PX200 engine in my GL. It's got a polini 208 with a 60mm long stroke crank. No base gasket. Reprofiled head with 1.5MM recessed. Squish is around 1.3mm.

Polini recommend the timing for their barrel with a standard crank is 19 degrees BTDC. I'm sure this would need to be changed because the longer stroke will change the port timing.

I'm having problems with 4 stroking just off idle, and just can't seem to adjust the jetting correctly so I'm thinking it might be caused by the timing.

Can anyone tell me what the ignition timing should be for this set up?