750ss 1994, With 1998 Monster Engine, Tacho Issue

Hi Jens,
I presume the Monster is from an injected bike and you using the 750SS wiring and ignition. It is possible to have the horizontal head machined to accept the mechanical tachometer drive from the 750. It's a case of drilling the blank boss in the head to accept the tacho drive but it does need careful alignment. I've had it done to an ST2 head.
There are various electronic tachometers on the market which get a signal from the switched side of one of the coils but I don't know which would work with the Kokusan ignition units of the SS. Something like this Smiths unit should work.

 

Which ECU and tacho are you using? Most Ducati ECU's with an RPM output will not work with an aftermarket tacho. Have you tried to connect your tacho to the low side of an ignition coil? Is the tacho configurable for 2 or 4 cylinder engines, etc.?

 

So no ECU but Ignition Control boxes.

As far as I can recall, when I wired an electric tacho on our race outfit; one wire took power from the ignition circuit (+ive) and another went to earth (-ive) and a third wire went to a coil on a piggy back connector, but I can't remember if it was the +ive or -ive terminal.

 

Yes, I used to have a VDO tacho like that. One wire to ign +ve, one wire to ground and the other took a feed from the switched side of the coil; the green/black of the horizontal coil or the grey of the vertical one which are both on the -ve side of the coils.

 

Ah well, getting the wires right helps
Idle speed should be about 1200 rpm + or - 500rpm

 

My 1997 750SS idled at 1050rpm when warmed up.