Won't upshift under load.

Do you mean you can\'t find 3rd gear or it won\'t shift into 3rd gear? If you can\'t find 3rd gear, shift all the way down to neutral, then shift up 2 clicks. On my Suzuki Boulevard S-50 (VS-800) the shift order is 1st gear down, then up for neutral, 2nd, 3rd, 4th, and 5th. Your crotch rocket probably also has a 6th. If the problem is that it won\'t shift into 3rd, then you had best take it to the shop as it is not readily repairable without specialized tools and knowledge.

it sound like it could be a vacuum problem. I have experienced this on cars i have worked on it usually turns out to be a vacuum problem 90 percent of the time.

Howdy: The 3rd and 4th gears are used the most, after awhile the dog and shifting forks get worn more. Try changing to Yamaha Lube simi-syn oil 10/40. Drain oil after warm up (get trans oil warm). The oil is in a silver 4gal containe at the Yamaha dealer. This oil has helped me.
Good luck - Doug

You have a couple of bent shift forks. This is a major repair job and not a recomended do-it-yourself project.

You have bent shift forks. I would replace all the forks in this case. This is a job for the shop. You would not want to tackle it at home. Most guys who do wind up taking a box of parts to the dealer. The repair costs more that way than if you just take them the bike.
Sorry for your problem.

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It sounds like the shifter pawl might not be centered. This is located behind the clutch basket and is a pretty big job to get to, easy adjustment just a pain to get to. You will need a manuel to do it yourself.

1st gear all the way down (toe shifter, not heel). Lift up N,2nd,3rd,4th,5th-6th(if applicable)