There does fell like a lot of slop when it is at top dead centre compared to my RB WS7 . A new pin or rod , it's only just run in but it could have been problems from new .
My friends run the same fuel and we get it at the same time and there's is fine , i go through a fair bit of fuel and race every 2 weeks so the fuel is turned over all the time .
I tried running it again today and went back to standard settings on the carby that is in the RB manual and still no difference , it was running at half to 3/4 throddle on the ground then it would just stop .