I have a Yamaha QT50 made in 1985 and I have a complete failure in the turn signal department. All of them look cosmetically fine but none of them work at all. When I flip the signal switch the display doesn't show that they have been engaged either. The headlight and taillight work fine but get brighter as the RPMs are higher like I would expect. Is there something that is broken that could affect all four lights like this?