Using an oilhead tach on my '92 GS

[DonW]

The tach on my GS crapped out a few months ago. 2nd or 3rd time an airhead electronic tach has failed for me. Don't really want to spend the money to have it rebuilt, as don't really consider it essential, just sort of interesting info.

But, I have a working tach from a '03 R1150RTP, and low and behold, the plug connections are identical. With a little gap filling work, I could fit this right in the same hole. Anybody know if the signal from the airhead electronic ignition will drive (accurately) an oilhead tach? I'm confused by the "lost spark" issue...

Also, I'd appreciate suggestions of other options. I've seen very small electronic (digital readout) tachs. Not interested in one of the older small add-on tachs like on the R80G/S, or earlier R100GS.

Thanks,

Don

[Major Softie]

Plug it in and try it!

I can't remember if my oilhead has a waste spark, but if it doesn't, then the tach will read twice as fast, which will be pretty obvious to you.

[Roy Gavin]

I have tried a few differnt tachos, but there just seem to be to much "background noise" on a GS ignition for a more modern tach, and they just wouldnt give a steady, stable sensible reading for any length of time, they just jumped all over the place.

But that may have been specific to my bike, so a test is gong to be the only way of finding out if yours does the same.

[Armaguidon13]

That's plug and play. It works as the original

[DonW]

Cool, thanks.

Don

[DonW]

Hmmm, problem. Good news- engine is back to running. Bad news- neither tach shows any RPM. Now I'm wondering if it is a wiring or other problem.

Is there an easy way to check, using a digital volt meter, if the tach signal wire is getting anything from the electronic ignition? Or a way to put some voltage on the tach itself and see if the needle responds? I suppose I could have two bad tachometers, but seems unlikely.

Don

[Kurt in S.A.]

http://bmwmotorcycletech.info/tach.htm

Kurt in S.A.