...on both cylinders! Driving a 16" x 8" Master Airscrew propeller, and its too small. I've found it labours when it gets hot, so I think the pistons may be expanding, reducing the clearance in the bore. Its not been up to maximum revs as I'm still trying to find the best carburettor settings.
I can confirm the pistons have expanded whilst hot as there are shiny areas on the sides where friction has occurred. I set them up in the lathe and machined off a minimum amount, just enough to clean the sides. The rear bearing had just started to break up, this is a very small bearing at 3mm id x 6mm od x 2.5mm tk. Part of the metal dust cage had come out and some balls were missing, so I removed the what was left and replaced it with a spare. Now in the middle of reassembly. Should have it running again soon.
Off to Cornwall this coming weekend, but I don't hold out much hope of having it ready in time. There's too much work to do on the aircraft (Ultimate Biplane).