Hi,
I have had trouble sourcing a replacement tachometer for my cb250N - not the item just the ridiculous price people have been asking...
Problem was the squared off section inside the tacho where the cable mounts into had been badly rounded by time or someone mounting the cable at an angle instead of straight - this caused the cable to round out the square hole...making the tacho not work at all..
I got two 1/2" lengths of electrical heat shrink, one over the other - pushed it down over the square cable end - shrunk it...inserted it properly and IT NOW WORKS...........cost $0.05....
it has lasted for two weeks so far...