I dont know what it is either, but the old honda motors never die. I have a 1967 Honda mini trial 50, never been rebuilt, never had any new gaskets, and motor never been opened. Basically all you have to do is change the oil every so often, that is the best maintenance a guy could do. Runs like a champ everytime! It sat in a barn for at least 15 years, I drug it out, put on new tires, chain, and cleaned carb, and purrs like a kitten. This was the first thing I ever rode and was about 18+ years ago! The body has taken a thrashing over the years, but the motor, let me tell ya..........
THE 80's RAGE! Currently owns:
81, 85 Yamaha Tri Moto 125
83 Yamaha Tri Moto 200 x2
82,83 Yamaha Tri Moto 175 project
85 Yamaha Tri Z 250
84 Kawasaki Tecate 250
84 Honda ATC 70
85 Honda ATC 350X
84 Honda ATC 250R
(2) 84 Honda ATC 200x
82, 83 Honda ATC 185s
81 ATC 200
Lots of other parts and bikes