It seems to run OK with the longer stroke than the bore I will fly and see how it goes , I will go up from an 8x4 to an 8x5 , the shaft is loose about 1.5 mm play at the end of a 9x6 prop , and its leaking out of the comp screw a little , Ive given it 5 minutes on a 9x6 , I will put it on the plane , starts OK
Ive got a lump of copper in the counterweight, as big as I can get, in and the piston is a lot lighter than stock , the stock piston is quite thick

rod is a lot thicker as I bent my first one as its only 2011 free machining aluminium so I made this one big ,

its out to 1.75 cc up from 1,5 cc 's
Also I made the inlet in the crank look like the inlet in my OS 15 , about the same timing roughly , and the piston is about 2mm longer with a smaller wrist pin

Wrist pin is 3mm down from 3.5 , piston is 0.7 thick down from 2mm , big end the same at 4mm , it got a reduced bore taper as the first try was too steep , its surging a lot , and getting hot , I dont want it to burn down , its fitted farily tight and needs a blow torch to heat it before starting , once its hot its OK , Ive burned a few fuel lines that way and had one fire , smothered with a big rag
I will give it another 5 minutes on the small prop before I fly, as Im good at cooking them before I get to the handle