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Discussion Starter #1
Front cylinder good spark and runs fine; no spark at rear plugs. I swaped front plugs to rear, still no spark at rear cylinder. I did the frame ground work at both coils and frame to ensure a good ground - no change. This started as a periodic problem before I put the bike away for the winter but now is all the time.

What do you suggest I check, and how...perhaps could be the rear coil??

I should add, I have 12 .3 volts at the battery prior to starting and about 14.5 volts idling on one cylinder if that helps.
 

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Pull the coils off and clean the surface of the frame and the coil bracket. Reinstall and check the wiring to the coils for good contact. It's free and could be the problem.

It was mine...
 

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put the back coil to the front and see if it has spark if it does not the coil is bad if it does than it is wirring or signal to the coil
 

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Discussion Starter #5
Thanks for the help...I ground off the paint at the coils, coil bracket and frame contact points last night with no improvement...but I'll try swapping the rear coil to the front and look for spark. I'll double check the other connections between the coil and the box too.
 
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Sled,

Run a jumper from the coil control wire on the ECU to the coil control connection on the coil. If the cylinder starts fireing, you have a bad harness wire (happened to me). You could then take an ohm meter and try to find the bread or just replace the control wire and run it outside the harness or if it is still under waranty you could get honda to replace it. Generally crappy grounds of the coil to the frame will not cause this to happen (the coils don't need the ground contact to the fram). If the coil is not working it will be either the common ground lead (black wire white stripe) or the control wire (yellow wire with blue stripe for one cylinder, blue wire with yellow stripe for the other cylinder). It could also be the ECU but I doubt it. Sounds like an intermittent connection.

Lonewolf
 

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Discussion Starter #8
I've finally got back to work on the bike. As suggested I temporarily switched the front coil that works fine to the rear with the same problem...no rear cylinder spark. I have good continuity between the hot blue/yellow wire at the coil and the ECU and the between the black/white ground wire connector at the coil to battery ground. I also put a jumper wire from the rear coil wire connector to the ECU wire just as it enters the plug in connector, no change in result.

So, it appears to not be a coil problem or a grounding problem and seems to be pointing to the ECU as the problem. Any thoughts on what to check next before I replace the ECU? How about reading trouble codes?

When this first started acting up last fall it was intermittent, primarily when I throttled down, the rear cylinder would cut out.

I did replace the alternator/generator stator about a year ago, could this have any influence?

Thanks for all the advice!
 

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switch bad coil with good coil still no spark. ck wire from coil to ecm ck good you may want to double ck that look inside wire connection at the ecm make sure pin is not bent or corroded or pushed in if wirring is good it will probably be the ecm if you have a buddy with a vtx ask to swap his ecm if you get spark there ya go good luck
 
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