I'm confused,as always..
Is this varnish buildup on the outside of the engine or inside ?
If its on the the outside has anyone one try to use Easyoff Oven Spray.
I use it to get rid of the heavy wood resin buildup on my saw blades
and router bits when I do wood work. I know it works on wood resin,
maybe it will work on the varnish. If somebody trys it,spray it on,let soak,
clean with a tooth brush.