Sunday, July 3, 2011

home made rev counter stuff

The plan: build a mechanical tacho and tach-drive onto an SS50 engine.
terms: do not use kitaco or takegawa bolt on stuff.

I started with a tach drive from a CB175, turned something on the lathe and took the teeth off of an old camshaft sprocket, this should be soldered together with silver and mounted to the camshaft.

should look like this when mounted:

The housing was cut down to remove unnecessary material and to create a hole for the bolt to go through that will hold everything onto the cylinderhead. A brass plug will be put in there with threads to accept the bolt.

One problem, on a CB175 this is on the right side of the camshaft, on the SS50 it will be on the left, so the tachocable will be turning the wrong way.

On the back of the Yamaha 600 guage unit (that I took the tach from for the RSC90) was an angle drive that I could use to reverse the rotation...

Some PVC tubing, a CB50 tach and one Yamaha drive later:

Testrun if it all works...NO?...
I looked at the angle drive the wrong way, so it doesn't actually reverse the rotation.
I will have to make something else to fit onto the modified CB175 drive and use this tacho on another bike when it is finished.
Will be painted black, alloy ring to be turned on the lathe and a piece of plexiglass to close it all up, after I've made a new face for it, probably upto 14000 RPM or a bit higher.


  1. Good effort, I also have a similar project (CB450 tacho), on hold :)

    What is the ratio of the Yamaha gearbox?

  2. yamaha gearbox is 1:1
    I believe it came off an FZR600 of the early 90's

  3. why dont you have the tachometer go in reverse? Pair that with a speedo, side by side, and have it rotate counter clockwise bottom up?