Originally Posted By: ZGRider
Any good synthetic 2-stroke oil at slightly leaner mixture will work fine. If the factory called for 32 to 1 ratio, then go to 40 to 1 and you'll be happy. Whatever you do, don't use "bean" oil in that old bike or you won't be happy.
What do you base this statement on? Frankly, being air cooled, and a piston port (no power valves here) a "bean" oil is a fine choice, especially if it's a little on the lean side. First, castor has an affinity for heat, actually being attracted to hot spots. As castor degrades through combustion, it reduces to platelets that keep on lubricating, eventually winding up as varnish. In a power valved two stroke, this means extra maintenance and a possibility of sluggish power valve action, causing power loss. But not so in the old GT Suzuki's. There have been many tests, both personal, and by two stroke tuners... castor makes more power for longer than any petroleum base, whether conventional, or ground up manufactured synthetics. The trade off is carbon and varnish. It is dirty oil, but the risk in this bike is minimal. Blendzall 455 is the only injector two stroke oil I know of. Common castor blends are not suited for injector apps, including Maxima 927, Castrol A747, Klotz BeNol, and Shell Advance M. All this being said, there were several runs on that GT380 mentioned where there was nothing but regular leaded in the tank, and 30 weight non detergent in the oil tank/ injector system.