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Discussion Starter #1
Slowly working through sorting out my badly running M 750 and I've rebuilt the carbs (full of sediment with some water in the float bowls) and tested the coils and ignition system.
All checks out. Put it back together. Still running very rough, but now the tach wants to run backwards!

Looking at the wiring diagram I can't see where the polarity for the tach is connected into the loom.

Anyone know where I've gone wrong?

Martin

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Discussion Starter #2
Testing the ignition system again and I think I might have a dodgy HT lead. Would that cause the tach to run backwards?

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Can't imagine a HT lead causing tach to run backwards,??
Replace them both anyway.
Tachometer takes it's initial signal from one of the coils though, maybe some wiring misconnected or shorting around there.
Check manual wiring diagram to check connectors are where they should be on coils.

Did it work normally before you started checking coils/ignition etc.
 

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Discussion Starter #4
Dived into the wiring last night. I remembered that a week or so before I had this problem the bike wouldn't start if the forks were turned full lock.
I dug around and found a damaged wire in the loom that runs from the start stop switch.
I switched around ignitors and leads last night and got no improvement so I'm thinking it's electrical but in the loom.
I'll start doing the tedious job of testing continuity of the various wires in the loom.
The tach issue might be a red herring and will be fixed once the ignition is fixed.
I suspect that the tach is not actually running backwards, but is just cutting out when the throttle is applied.

Martin


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I would first remove some of the plastic covering where the cut wire is. Sounds like either broken wire and/or shorting out.
Fix the broken connection and check other wires in that area. also possible reason why, wires don't usually just break, something contacting there. Could fix the other issues.
 

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My wire broke there as well.. I was practicing full lock turns and “slow race”, and then the next day the bike would die turning the bars

Mine is close to the same bike, 2000 900ie
Copper work hardens then just brakes if you bend it over and over .. it was only held together by the insulation

I didn’t have any other problems other than the bike not running though..
 
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