[psm]

I just picked up a 94 Yamaha Vmax 500. It had been sitting for a few years (with the occasional run up). Took it out a few times and noticed it bogging down when full trottle is applied. If I give it half throttle its goes good. Once accelerated at half throttle if I give it anymore it boggs down again. Ive tried all grades of gas with no noticeable difference. Any ideas?

 

[dl_sledding]

1. Carbs/Gas/Oil: Have you cleaned the carbs, and replaced the gas and oil?

2. (My bet) Drive belt: this problem sounds like a classic worn/stretched drive belt. Also, going along with this, possibly clutches that need cleaning.

 

[psm]

Thanks for the reply. I took the carbs off today to clean them and found one neddle jet was stuck. I poped it out and noticed some scoring on the neddle jet and cylinder wall of the carb. Any idea if the cylinder wall can be polished? I polished the neddle jet with crocus cloth but can't get into the cylinder. By the way, one of the main jets had a little bit of scum in it.