1981 honda cb750 custom

[ken86]

i am looking at getting a 1981 cb 750 c. i want to do some upgrades and i am looking a gauge and it has a gear indicator on it can you set that up on this year bike. if so how hard is it to do.

[sgtslag]

The gear indicator device requires a signal from the transmission, or an electric signal from  the tachometer, from the Electronic Control Module, on an Electronic Fuel Injected engine (computerized).  The EFI engines have a number of electrical signals available to trigger things, which your bike does not have; no computer, no signals to trigger the gear indicator.

Can it be done?  Yes.  Is it easy?  Nooo...  Sorry.  Cheers!

[ken86]

How would you'd do it if you have done it. Or if I get one with it does it need to be set up for everything else to work.

[sgtslag]

I have not done it.  I looked into it, but I gave up on the idea, as the need, for me, anyway, was outweighed by the cost in both time, and money.

The gear shift indicator senses shifts through the RPM changes of the engine.  On a system which has no electronic triggering, you might be able to make it work off of the ignition timing pulses -- effectively similar to RPM's, and the pulses sent by an ECM or an electronic tachometer.  This could best be done with tapping into the low voltage side of the ignition coils.

It would require the assistance of an Electronic Technician, an Oscilloscope, and some other test equipment.  It would not be terribly easy, nor terribly difficult (I believe the pulses would need to be divided down by two, to equal the RPM's).  It will, however, be time-consuming, as it is custom design work, and time is money.  Cheers!

[sgtslag]

I visited the gear indicator web page, downloaded the instructions, and I discovered that it requires an electronic speed signal, in addition to the electronic RPM signal.  They offer a kit to supply this, but it is still quite involved to make it work with a bike without an on-board computer.  Here is the link to their instructions PDF.  Cheers!