On Friday, May 15, 2020 at 11:34:29 AM UTC-4, john firth wrote:
Amongst all the weighty deliberations on improving safety,
maybe someone experienced and knowlegable about diaphrgam carburetors
could give me guidance.
I fly a PIK 20E , Rotax 501 unreliable engine which has been behaving erratically, surging but not misfiring that I can detect.

From the plugs I see rear cyl lean, front cyl a bit rich.
Does a split carb diaphragm enrich or lean the mixture?

thanks

John F

An air leak was found at the shutoff valve , and fixed.
The carbs were pulled and the diaphragms examined; one is a bit stretched
but no holes found. Search for Tillotoson HC spares unsuccessfull.
Rebuilt everything with diaphragms swapped.
Engine now runs smoothly slightly lacking full power.
Rear cyl still hot as shown by EGT.
JMF