Re: heavy riders
If your handy with a dremel a little port work can go a long way. also get some wet/dry sandpaper and a piece of glass and carefully lap the head and the top of the jug, they are notorious for being uneven and cause head leaks. I used some kerosene to lubricated the paper. Another real common mod that helps is trimming the piston skirt. put the piston to top dead center and draw a line on section of the piston that is obstructing the intake port, you will have to take off the intake to do this, then remove the piston and carefully trim the skirt up to the line you made so the port opens fully. A good spark plug and boot will help too. Fleet farm sells good silicone wires singly for 3 bucks or so.