1983 KZ750 H4 Tachometer not working correctly

So I'm cobbling together a working bike out of two - the 1983 and it's 1981 sister. The tach on the '83 was trashed in a wreck (thought the bent needle still functioned as expected).

No problem, right? Just pull the one off the '81 - it worked fine last year when the '81 still ran.

Except now, it doesn't work right... it is sluggish. It eventually registers the correct RPM (thereabout), but it is SLOW getting there. Moves up AND down VERY slowly. I tried replacing the cable with the '81 cable, but that had no effect.

Any ideas?

If your tach is the same as the one on my 1980 750/4 then the upper and lower halves are held together by that chromed ring around the middle. Cutting the ring with a Dremel or a hacksaw blade will allow you to separate the upper and lower halves. There's not a lot inside the tach and there could be some dirt or cobwebs in the works . Perhaps the workings need a drop of machine oil. Putting it all back together again I used epoxy on the ring and a large hose clamp to hold it in place while the epoxy set. There will be a seam but if you work it so that the seam is at 6 o clock then it will be barely noticeable.

Before you go that far though I think I'd try blowing compressed air in the holes where the bulbs go etc and see if you dislodge any dirt

Good luck

OK, I went all lazy and stuff... after I got the chain adjusted, I took her for a little ride (about 5-miles). My the time I got back, whatever was stuck in the tach must have blown out, as it is working perfectly.