I'm in the process of repairing a Summit 800R belonging to a local sporting estate, (low compression one cylinder requiring a top end rebuild), and now all functions correctly but for the tachometer.
The Wh./Gn. wire from pin 12 of the ECM plug to pin 7 of the tacho. plug is intact and with the engine running and tacho. disconnected I get no voltage on pin 7, neither AC or DC, with the negative meter lead to earth.
Similarly connecting a 12v. battery to pins 8 and 11, +ve and -ve. respectively then tap a +ve. via a test lamp to the RPM input pin 7 there is no needle movement.
What format is the RPM signal from the ECM to the tacho. ? Varying DC or digital pulses ? To test for the latter would require me to fire up the multi chann. Tektronix oscilloscope which is a wee bit of overkill.
Similarly what format is the actual tacho., an analogue voltmeter or a pulse sampler similar to the Krober / Motoplat as used on racing motorcycles ?
Incidentally all the lamps function as designed on the tacho. and the LCD display with the engine running.
As this model is a pull start and I'm incapable of working the manual start I've made a temporary power start using a DeWalt cordless drill with a 7/16th. Whitworth socket on the end of the drive pulley bolt .
Any help gratefully appreciated by this newcomer to this site