by loucrane » Tue Apr 15, 2008 9:40 am
Jerry,
I haven't yet done it, but I hear from good folks that you are looking the right direction with the methanol-based fuel. It can run cooler, and will probably run less time per ounce. (Those are connected ideas: the alcohol chills things nicely as it evaporates, and as it has less potential heat per unit of volume/weight, you need to flush more of it through for similar performance.)
Also, minimum of 25% castor in the fuel, with as much as 30% a decent idea until you are sure. Alcohol doesn't mix well with mineral-based oils. If everything looks good, but you suspect a tendency to varnish or gum from the castor, 1% or so of a synthetic, like KLOTZ, might keep things clean.
Some have tried a few of the highly advanced synthetic oils newly available, and speak well of them. Your Bunch Tiger was designed when castor was one of the best choices for oil. Finding a good single-weight SAE70 is not too easy, and would work best in a gasoline-based fuel - defeating your purpose to run it gently and cooler.
Luck, and let us know how things progress?