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Discussion Starter · #1 ·
My 2007 sabre 1100 has just the same issue. Runs great till just under 4000rpm then starts missing badly. It is bad in 1st and second. Changing up a gear reduces rpm and fixes it till 4000rpm is reached again. I've changed plugs, leads and cleaned out and balanced carbs etc to no avail. Also changed fuel filter and checked fuel pump. I'm a bit baffled by the issue. I still ride the bike but if anyone has any ideas about what to check out next I'd like to hear them.
 

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I'd be looking at the wiring from the ignitor coils to the ignition module. This is a low voltage pulse and would be degraded by high resistance connections. There were two connectors inline on my Shadow and most of the wiring run lives down in the heat, oil and grime. If the ignition module is counting pulses, when these get closer together at high rpm, they can start blending into each other if signal to noise degrades.

Another idea, (and these are just ideas, theory, not experience), would be to look at the quality of the DC. If the rectifier is passing any AC, this can confuse an ignition module or ECU. Similarly, if a ground or B+ connection is intermittent, DC might be spiking all over the place.
 

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Discussion Starter · #3 ·
Thanks. Are you talking about the thin wires coming off the coils down to ignition module ? Also I had another thought....could wiring the tacho on to the coils possibly cause an issue. These after market universal tachos made in China may not be best of quality.
 

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I was talking about the pickup coils that sense the toothed ring that spins with the crankshaft. I've seen them called "ignitor coils" and "pulse generators". These put out low energy pulses.

The ICM makes sense of those pulses and puts out a LOT more energy to the ignition coils, so an additional load on the primary of the ignition coil shouldn't be a big deal, in my opinion. In fact, this ignition coil primary circuit is used to trigger what is called the "fuel pump relay" on some Shadows.

The best check to determine if an add-on tachometer is causing issues, would be to remove it and see if the problem goes away.

For finding problems like this, a basic two-channel O-scope seems like a good tool to have. DS212 Mini Pocket Size Portable Handheld Mini Digital Storage Oscilloscope,with 2 Channel for Electronic Maintenance, Electronic Engineering,Testing equipment11: Amazon.com: Industrial & Scientific
One could tap in and monitor signals at various points in the chain, and see where the problem is occurring. Personally, I'm always happier to buy a tool to help me diagnose a problem and know exactly what the issue is, rather than substitute parts until I hit the right thing. Maybe changing the ICM or the pulse generators will fix the problem, but what one will never realize is that just disconnecting and reconnecting the connectors, and thus wiping off the oxide layer, would also have fixed the problem.
 

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Discussion Starter · #5 ·
Ok. I'll first disconnect the tacho wiring from the coils and see if that does any good.
If that fails to fix it I'll clean up the ICM wires and connectors. Thanks for the advice.
 

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Discussion Starter · #6 ·
Well. I decided not to bother disconnecting the tacho since I'd soldered the wires together and I was starting to think that wasn't the problem. Next up I found the ICM. It was pretty filthy so I cleaned up the wiring and cables going into it. After that I opened the thing up. It was actually dirty inside. I cleaned it all up in there with spray on elec cleaner and carefully blew it out with my airline. Put it back together and took tha bike out to check it. Seems to have done the trick. It now goes up to about 5800rpm before playing up as opposed to 3900 which it was doing before. This appears to be when the throttle cut out comes in. All good as far as I can tell.
I've read about numerous riders having the issue I had. Maybe my fix will help someone else out. BTW the ICM is in a pretty stupid place on the bike. It's obviously likely to get dirty and wet where it is.
 

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Congratulations on finding the problem and thanks for posting the solution.
 
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