Exciters-Power Jet

[Black Bear]

Folks,

I have removed the Power Jet circuit on all of my exciters as it is has been referenced in the technical bulletins. I am however note quite sure I understand the true technical reasoning? Can someone without to much effort explain how it relates to lean operation or other problems that Yamaha needed to eliminate.

 

[Throttle Junkie35]

I cant give you a real answer, but I have heard many things over the years as to why they had the update. I believe they were having harmonic problems with the engine that was causing the fuel to foam in the float bowls causing a lean condition. I believe in 1989 or 1990 they went with a heavier flywheel to help this issue. They also did away with the PJ carbs in 89. I believe the carb update was a preventative measure (warranty issue) on the 87-88's to remove the power jets as well thinking they (Yamaha engineers) had a jetting issue. This is pure speculation as I have read many, many threads and articles and talked with a lot of mechanics over the years. It would be fair to say it's a really good educated guess on my part.
I have have no problem ditching the pj's on my exciters because by the time I usually take ownership of them, the bowls are full of solid crud, and the o-rings are usually shot. LOL.