I am doing my own Fuji 80 projects here, so I've been looking in to it. The book says 30wt non detergent oil.
The reason they stipulate non detergent is that this oil allows particles to settle into the sump. Same reason Briggs and Stratton used to specify it. Detergent oil keeps particles in suspension, so they can be filtered out. The non detergent oil is becoming harder to find, if not impossible in some places. Tractor Supply had it in my town.
You won't find a ton of knowledge or information out there on these engines. Something I have read on Hodaka forums however is that it's permissible to use the current 75wt gear oils designed for two strokes with wet clutches. Since I am now on my eighth attempt at removing the clutch to figure out why it wont disengage, I have drained the oil that many times. Once I figure out this odd phonom, I will replace it with 1.5 pints of modern 75w two stroke lube.
I mixed at 20:1 and it's running great with 91 octane no alcohol gas. It starts cold by about half a kick with a flip flop. Best running two stroke I've owned. Just doesn't clutch worth a damn.
Note that engine was used on a lot more than just Rupps. I have a couple of manuals coming in, and I will be building at least another engine, so if I learn enough to garner proper torque for the clutch nut, I'll be an expert.
Thanks for your reply Havasu Dave, My next question is... I am assuming that one of these grease fittings also serves as the drain plug. The pink in the background is from my wife's 1977 VW Beetle. Yes, I painted it pink for her!
First bit of literature came in, and it cost me $40 to learn that the clutch nut is 250 inch pounds, and that I have assembled everything from the output shaft to the pinion gear and all of the thrust washers and shims correctly, and the reason my clutch wont disengage is due to FM. (Fricking Magic) Maybe an Ah-Ha moment costs more than $40.
As part of that $40 expenditure, I learned that the non-detergent 30wt oil quantity is 1.25 pints. The lower line is one pint, and the upper 1.25. Break in oil to fuel ratio is 16:1, but after that, it's 20:1 just like I guessed. (My arm got sore patting myself on the back for being such a great guesser)
Some folks like to add ATF before a gear oil change to flush the impurities before an oil change.
I have a lot more specifications for the mounting dimensions, and some servicing information and even a service bulletin. Shoot me a PM if you have any further questions on any of this or that.