Bizarre 1200 Bandit ignition fault.

I've clipped a strobe to each ignition lead on the Bandit, lead 1 has a nice stable flash flash flash flash etc... all the others seem to have the flash flash interspersed with some sort of fibrillation like the flashes increase three fold, then drop back to a couple of solid, well times flashes, then back to the erratic flashes.

The effect of this on the running is that it will run nicely for a few minutes, then it just goes "durrrrrr" and then it's back up again, it's like a switch being flipped on and off between perfect running and running on 3 cylinders.

Coils and leads have been replaced with Dyna/Taylor leads and the bike was doing this with the old coils on.

I'm thinking ECU, any thoughts?

I'd doubt it's the ECU as that only sees a pair of coils, so if it was giving a faulty output it'd affect (checks with moth - yep, Affect) either cyls 1/4 or 2/3, not just one of them.

But as you've replaced everything downstream of the ECU ..... ?

Float heights/float valve sticking shut until the bowl's almost empty?

Originally Posted by fastfitter

I'd doubt it's the ECU as that only sees a pair of coils, so if it was giving a faulty output it'd affect (checks with moth - yep, Affect) either cyls 1/4 or 2/3, not just one of them.

But as you've replaced everything downstream of the ECU ..... ?

Float heights/float valve sticking shut until the bowl's almost empty?

Carbs all good, stripped, cleaned, floats measured.

Checked the crank sensor?

Would be worth checking the resistance on the coils to see if they were breaking down.

brand new coils, brand new leads.


Kat, pickup is on the suspects list.

Originally Posted by Zanx

brand new coils, brand new leads.


Kat, pickup is on the suspects list.

When you check, wiggle the wire as mine took an age to diagnose as a damaged wire.

Kat, im going to replace the whole lot i think, Dyna 2000, that way the entire system from pickup to spark plug is Dyna. it plays up on the road too, runs on what feels like three cylinders till the turbo spins up, then it all goes into the future.

were the plugs + caps also replaced?

check the engine main earth. the bike has a lot of work done, check the earth points aren't painted (you'd be surprised)

bizarre that it would be just the one lead not giving trouble rather than a pair.

isn't it / wasn't it so that bigger Suzukis have a TRE and it cuts ignition on a certain safety circuit? maybe that's being engaged? [/guess]

might be worth altering the routing of the HT leads, theres an effect known as inductive firing or cross firing where adjacent leads pick up enough energy to give a weak spark. It can happen where there are long runs in parrallel, especially if they are clipped to a steel frame tube.

Originally Posted by a_morti

were the plugs + caps also replaced?

check the engine main earth. the bike has a lot of work done, check the earth points aren't painted (you'd be surprised)

bizarre that it would be just the one lead not giving trouble rather than a pair.

isn't it / wasn't it so that bigger Suzukis have a TRE and it cuts ignition on a certain safety circuit? maybe that's being engaged? [/guess]

New plugs, new leads and caps. The bike has an air shifter, I'm wondering if one of the nasty blue crimp connectors isn't playing up. And yes, seems odd to be on one cylinder and not the others.

Originally Posted by Big Pete

might be worth altering the routing of the HT leads, theres an effect known as inductive firing or cross firing where adjacent leads pick up enough energy to give a weak spark. It can happen where there are long runs in parrallel, especially if they are clipped to a steel frame tube.

Not much I can do with that, I've trimmed the leads to reach perfectly. Might try shielding the main offenders though.

Originally Posted by maccecht

Would be worth checking the resistance on the coils to see if they were breaking down.

Originally Posted by Zanx

Coils and leads have been replaced with Dyna/Taylor leads and the bike was doing this with the old coils on.

Apologies I read it as it only done the weird shit with the old coils on and you had replaced them.
Check you have good clean earths on both coils and check the spade connectors have good clean contacts and the wires into the spades are well seated. Still check the resistances that are specified. Being brand new does not mean they cannot be faulty. Iron out all the obvious possibilities first.

Originally Posted by maccecht

Apologies I read it as it only done the weird shit with the old coils on and you had replaced them.
Check you have good clean earths on both coils and check the spade connectors have good clean contacts and the wires into the spades are well seated. Still check the resistances that are specified. Being brand new does not mean they cannot be faulty. Iron out all the obvious possibilities first.

Valid points, I'll check the earths at the weekend.