Motorcycle Repair: 1974 yamaha dt100 enduro, yamaha dt100, clutch cable

Question
First, I would like to thank you for the help you gave me reguarding the fuel system that was great and now my next question I drained the trans fluid and took the case off to check inside it all looked perfect so after not touching a thing under the case I put it back together I went to my local Yamaha dealer for oil for the case the kid at the parts counter had no idea what to give me he told me to use hp Honda trans fluid it Was 80w/85w i put it in checked the level on the dipstick and fired the bike up put it in gear and almost instantly the clutch was slipping wouldn't change gears while riding it was all jacked up so I called and talked to a parts Guy who told me the weight was to heavy and to use regular motorcycle oil 10-40 so I drained the case and changed the oil fired it up let it warm and same issue. before the original fluid was drained the bike ran fine the clutch was a little worn but in a "very broke in" kinda way no slips she cycled through the gears with no issues any ideas what could be going on? Any idea what the corect oil and capacity would be? I would very much appreciate the help thanks in advance-james

Answer
James,Some of the Belray and Maxima MTL oils have a viscosity of 75-85wt this is not uncommon. Now if the oil in to slick it can cause the clutch to slip. Some individuals have put in a good 20w-50 motor oil and this will work also. Make sure that once the oil is in the crank case that the clutch cable is adjusted right. If its to tight it wont let the clutch release completely and allow it to slip. Loosen the handle bar lever so that there is about 2mm gap at the outer edge of the lever and the perch before the clutch cable actually pulls the clutch. There should be the feel of some resistance of the clutch with the lever slightly pulled.