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You are having a loss of primary ignition if your tack is loosing it's signal at the same time. The tow most probable causes are the safety (sidestand) relay or a break in a wire coming down the stearing head.

 

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The loss of power on his along with the loss of tach would say a bad coil to me.

I'm with Howie on this one - the tach feeds of the low voltage side of the coil so a bad coil is unlikely to be the cause given the stated symptoms.

big (besides, I've got first hand experience with broken wires in the loom at the steering head...)

 

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Duckpainter also has a good point about the ignition module connector. It could also be that module. Knock out one cylinder and there is the symptom. Check the connector. If the problem still exists, switch modules. Same symptom but the tach now works, bingo!

 

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How is a bad coil unlikely if there is a significant loss of power. Bad wiring at the steering head would not explain a loss of power.

I was speaking from personal experience with my 01' 750. Sitting on the bike the coil on the right will cause loss of tach and one cylinder from a poor connection on the bottom of the coil.

If you loose electric supply to the bike through the wiring in the steering head you will have no ignition or tach since...well...there is no electricity. It is basically the same as hitting the kill switch. There may also be no lights, but the operator may not notice this during the day time. No tach signal means no low voltage signal to the coil so that coil would not function. Could a bad coil or connection at the coil cause a loss of a tach signal? Possibly, if this would cause the module to malfunction, ie. the transistor nit triggering due to an open circuit. I can't determine this without a schematic and maybe more for the module.

 

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How is a bad coil unlikely if there is a significant loss of power. Bad wiring at the steering head would not explain a loss of power.

My reasoning is that the loss of power is due to a loss of sparks, but that if that's caused by a bad coil then you're assuming the low voltage side of the ignition electrics is still working properly - if that was true you'd expect the tach to work as normal. Since the tach isn't working normally, that could be explained by problems in the low voltage side of the ignition.

I was speaking from personal experience with my 01' 750. Sitting on the bike the coil on the right will cause loss of tach and one cylinder from a poor connection on the bottom of the coil.

Yep yep - you're talking about a connection problem on the 12v side of the coil, not an actual "bad coil".

I'll defer to your experience here, my '99 M750 has no tach, I'm just theorizing and trying to deduce likely problems... Bob22 - here's a good first place to start looking.

big