M750 WITH SPARK ON ONLY ONE CYLINDER....HELP

[fstdy]

I have a 2001 M750 that only has spark on one plug. I tried swapping the two coils. No change.

Tried swaping the CDI black boxes, No change.

Tried swapping the 3 wire connectors between the black boxes, no change

Tried swapping the 2 wire connectors(pickups) between the CDI black boxes, no change

Measured the ohm's coming from the ignition pickup wires. Both measure 100 - 105



Switched the wires going to the coils and it follows the wires.

If I swap just the red wires going to the coils there is no change but if I change the single wires going to the coils the problem follows one of the wires.  There is no apparent damage to any wires.

I dont know what else to check

Any ideas??

[Howie]

One item makes no sense.  If you switch the pick up leads you are radically messing with timing so I do not understand how the bike can be running the same.  The red wire you are talking about comes from the kill switch and powers both the coils and modules.  You didn't say which cylinder is not firing, but there is a break in the wire somewhere.  If you have an owner's manual the wiring diagram will help you.  If not, go to  http://www.ducati.com/services/maintenance/index.do  and download it.  Why two posts for the same problem?

[fstdy]

Thanks Howie. I wanted to put all the updates in a new post.

What I mean by no change is there is no spark from the plug. I am not trying to run the bike during all these tests. I simply have both plugs out and watch for spark from either plug.  It only changes when I swap the single wire (not the red ones) between the two coils.

It is the rear cylinder that has no spark.

[fstdy]

Problem ended up being the tach. Followed the grey wire the problem followed and it led to the tach. Unplug the 3 wire connector on tach and cyl started to spark! Tach was out of a 750SS and although has exact same connector/wires it apparently is not compatable.

I swapped this tach out months ago when I first stared my restore on the bike I had just bought. So with the tank off getting painted I didnt try to run the bike with the new tach.

Thanks for link to manual. thats how I found out grey wire leads to tach!!

Silly!!

[Howie]

Was the tach working?

[Duck-Stew]

Tachometers off 750SSi.e.'s are designed to run on one pulse per cam revolution.  Carburated models run 2 pulses per cam revolution.  Even if it were wired up correctly, you'd have to address this issue for it to read correct RPM.

Glad you figured it out! 

[fstdy]

So anyone know if gauges(tach) off a 98 M900 will work on my 01 M750?

[Duck-Stew]

Tach off a 1998 M900 would work on your '01 M750 as they're both carburated, but the '98 M900 didn't come w/a tachometer from the factory so it's an aftermarket unit.  Not that it's an issue, just an FYI.