Check very closely where the bearring sits in the aluminum case, if there are a lot of miles on the eigine, or the main bearrings were installed incorrectly at one point, the alumimum case can crack all the way around the bearring. Look for a hairline crack around the bearring. Just an idea I came up with after splitting cases on my 81 Yamaha IT 175, and seeing this on both sides. I know its a different engine, but just a thought. ---- Jon.
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