Speedo acting up

[AirRsq]

FYI: your stop/turn/tail/horn fuse has some odd connection to your speedometer. Not sure why or how, but...

Story...

My speedometer was reporting very erratic readings during a track day this weekend - jumped around, read very low speeds when 6th gear WOT, etc. I had just completed the 600 mile service and I assumed I damaged the ABS connector during my 'big hands in a small hole' work on the top of the engine. After inspecting the speed pickups on the front and rear wheel for grease clumps, damage, etc, I started to tear the tank off and inspect the harnesses I had bludgeoned during the valve check. Before I dug too deep, I decided to throw a 'hail mary' and put the fuse for the stop/turn/tail/horn back in that I had removed as a track prep...and...voila!! WTF? I never would have imagined any possible connection between these circuits and didn't even consider putting the fuse back in at the track. Still scratching my head, but at least the problem is solved.

Oddly, the mileage still seemed to accurately count

 

[lok]

Same thing happened to my rc390. Plugged the fuse back in and speedo is back to normal.

Strange.

 

[ReidMcT]

This little thread has saved me a lot of fruitless troubleshooting on my dedicated track bike. The question now is: Can the speedometer be made to behave with the lighting fuse removed? I'm guessing not, due to CAN-bus mysteries.

BTW, I surely am getting annoyed at the number of things not covered by the workshop manual. No wonder so many KTM technicians seem so poorly trained: They lack proper training materials!

edit: Having glanced at the electrical schematic, it looks like there's no hope of remedying this issue, short of hacking the ECU. I guess I now must choose between no speedo, or disconnecting a few more plugs. I dislike leaving things unplugged, but I suppose I'll go that way, and just wrap them as best I can to keep them clean. Or will unplugging them throw CAN-bus errors or lights-out warnings? I guess I'll find out.