I use VR1 20w50. Heat is the key. I get mine up to 210 or so . Best if you can run a primer plus. But you can't do that with stack injection, so a squirt or two of gas into the stacks and alky off will help clear it. Your system may need some time for the lines to empty, like mine. I have to wait for a minute, crank with ignition on and alky off. After it will no longer fire, then squirt a little gas in it and crank some more. Use of fogging oil might be a help in keeping the bores in nice shape between races.