Hi I did use a degree wheel and have it set a 30 degrees dtdc.As far as the piston it is a two ring and i am going to order a new piston and also get another wt 499 carb and see if it brings up the rpm.Now on my gas to glow ryobi with a new piston and carb it will tac at 7400 rpm. What plugdoyou all use for the xyz i am using a chapion rd7j gapped at 20. does that sound about right? michael