i had a kawasaki er5.. i bought an aftermarket speedo for it i remember when i wired up the tacho to the original tacho wire it would read double, saying 6000rpm when i was only doing 3000rpm.. not sure if its the same on these bikes. but to solve the problem, i had to tap into one of my coil packs. not exactly sure how it would work on these bikes.. maybe that will give you an idea of something?