there is no such bike yz490 didn't start till 1982 and went on to 1990 before this it was a 465 ....
739 ft lbs of torque
Float height=23mm,(0.906+-0.02 in) idle speed1100rpm.
40 ft lbs
22 to 25 Ft/lbs
17.00 HP (12.4 kW)) @ 7500 RPM according to manufacturer specs for 1980
The Specs was created in 1980.
my book says 15 lbs then back off just enough to line up cotter pin
The Yamaha 850 XS is an air cooled bike. There is no radiator to fill.
If you are talking about the 1980 Yamaha Enticer, the top speed would be 55mph.
On a Yamaha 1980 XS400 the valve clearance for the inlet valve should be 0.0003 inches. The valve clearance for the exhaust should be 0.006 inches.