GSX750ESD Getting Wierd

[Dak S83]

Damn this thing, it's getting strange, OK, everything checks out OK, coils, igniter etc. We still have no spark BUT if you are winding it over there is no spark but just has you let the starter button go if the engine is still winding a bit and is in the right place it sparks, a nice big fat blue one. Also the battery voltage, brand new battery, is reading 12.7 volts. When winding the voltage being supplied to the igniter drops to 9.5V while winding over, I've checked the main fat earth cable attached to the engine, that's all good but the other thinner earth cable disappears into the loom somewhere, as far as I can tell there is no other earth connection on the frame etc. Any ideas? It's doing my head in.

[sidecar bob]

Have you checked the pickups & made sure the trigger is tight on the crankshaft?
Does flicking the killswitch off & on create a spark?

[sidecar bob]

Break it down, Is the trigger doing what it should, pickups? Are they clean with correct air gap & tight? Wiring connectors from pick up to loom? Wiring to igniter (ECU module) Wiring to & fro killswitch/ignition switch? power to module? Constant Power positive to coils, power switching negative to coils.
Is the starter drawing so much current that it's robbing the ignition system of sufficient voltage to make sparks?
Have you tried pushing it to see if it sparks, especially at night with all the plugs out?

[pete376403]

Coils wired to the wrong side of the starter relay or solenoid?

[Dak S83]

Heya mate, yup done all the above except trying to push it, ain't fit enough to do that, you'll see why if you call in. Gonna give it a rest and attack again tomorrow. I'll bet my left testicle it's something simple and stupid. Flicking the kill switch does not produce a spark, which is weird, I think according to what I've read it should.

[MarkW]

Several thousand years ago my 1981 GS450 twin had a similar problem and it turned out that the very elderly starter motor was drawing way to much current, it would crank but the voltage drop, even with a good battery, was such that the ignition wouldn't fire anything. When the motor was spinning and the starter button released the inertia in the motor meant that it spun over for another revolution and there was a big fat spark because for that tiny spot in time the starter was no longer drawing the current. Bump starting was simple [no starter current draw] and the problem went away when the starter motor was replaced. I don't know if you could test this by using a jump battery for the starter only and the standard bike battery for the rest of the electrical system - hooking the jump battery positive directly [and temporarily] to the big positive lead from the starter solenoid to the starter to turn the bike over.

[SaferRides]

Sounds like the igniter is not getting enough volts. I had the same thing with a tired battery on the ZZR1200 - it would crank the engine but not start it. Jumpered another battery and away it went.

Did you charge the new battery? Lead acid batteries are only partially charged out of the box.

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[Dak S83]

Several thousand years ago my 1981 GS450 twin had a similar problem and it turned out that the very elderly starter motor was drawing way to much current, it would crank but the voltage drop, even with a good battery, was such that the ignition wouldn't fire anything. When the motor was spinning and the starter button released the inertia in the motor meant that it spun over for another revolution and there was a big fat spark because for that tiny spot in time the starter was no longer drawing the current. Bump starting was simple [no starter current draw] and the problem went away when the starter motor was replaced. I don't know if you could test this by using a jump battery for the starter only and the standard bike battery for the rest of the electrical system - hooking the jump battery positive directly [and temporarily] to the big positive lead from the starter solenoid to the starter to turn the bike over.

Mate, that's exactly what I'm beginning to think, the voltage supply to the igniter when cranking drops to about 9.5 volts which I'm thinking is not enough power for the igniter and coils, the voltage supply to the coils drops to around 9.5 volts also while cranking.

[Dak S83]

Sounds like the igniter is not getting enough volts. I had the same thing with a tired battery on the ZZR1200 - it would crank the engine but not start it. Jumpered another battery and away it went.

Did you charge the new battery? Lead acid batteries are only partially charged out of the box.

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Yup, brand new battery was charged overnight on a smart charger. Yea, this is what I'm beginning to think, read my above post re voltage dropping.

[Dak S83]

IT'S ALIVE, well sort off, carburetors are a mess from sitting for three ish years. Well today I decided, after looking at the wiring diagram, the kill switch is what supplies power to both the igniter and the coils, that's all it does oh and to the start solenoid as well. Pulled the right hand switch gear apart and unfortunately the switch itself cant be pulled apart to clean the contacts but after a spray with contact cleaner and CRC I put it back together and what do you know, after a bit if fired up, only on 3 cylinders though due to the carbs. So off come the carbs, holy sheeeet, they are a mess, green goo for miles, number 3, the cylinder that wasn't firing is the worst by far, pilot jet was completely gooed up the the jet needle was even jammed in the emulsion tube, so off to someone tomorrow that has an ultrasonic cleaner I think. So after all that I think a bit of dodgy wiring and corroded kill switch that's all that's wrong with it. Oh, it fired up with the original HyperPak igniter too so thats a bonus, it's good after all. Attached is a pic of the abortion wiring job someone did to connect the HyperPak unit, why they did this I don't know as they use the OE connectors.

[sidecar bob]

Wasn't that the first thing I told you?:msn-wink:
Get rid of those god forsaken blue "car mechanic terminals" for fucks sake.

[F5 Dave]

Oh jeezuz, Pre-insulated terminals. Pre-destined to fail.
I'd still consider the switch an issue, once dry check for voltage drop again.

[Dak S83]

Wasn't that the first thing I told you?:msn-wink:
Get rid of those god forsaken blue "car mechanic terminals" for fucks sake.

LOL, they are gone mate, along with the stupid orange screw block connector you can see hiding there, who ever did that job needs a frikkin bullet. Lets just say when it goes back together with clean carbs it better bloody go.

[Dak S83]

Oh jeezuz, Pre-insulated terminals. Pre-destined to fail.
I'd still consider the switch an issue, once dry check for voltage drop again.

Yup certainly will do. All going to plan hopefully might be able to ride it this weekend.

[sidecar bob]

Part of washing my bikes involves blowing out the switchgear with compressed air, followed by a ride of up to 100kmh for a few minutes.

[Grumph]

There's a well known mod for elderly bikes with voltage drop problems. Simply insert a relay so that the switches - ignition and or kill switch - activate the relay and send 12v direct to the coils. Gets rid of the voltage drop through old switchgear.

[Dak S83]

There's a well known mod for elderly bikes with voltage drop problems. Simply insert a relay so that the switches - ignition and or kill switch - activate the relay and send 12v direct to the coils. Gets rid of the voltage drop through old switchgear.

Good idea and yup, done that before on cars.

[Dak S83]

Part of washing my bikes involves blowing out the switchgear with compressed air, followed by a ride of up to 100kmh for a few minutes.

Yea mate, that's what I usually do as well, as well as draining the carbs if it's going to sit for a long time, which I didn't bloody do on my other bike due to me getting real sick, ie nearly dying. So now have that bike to do a carb clean on as well, and that's a nightmare to pull the carbs on, 2006 S83

[SaferRides]

There's a well known mod for elderly bikes with voltage drop problems. Simply insert a relay so that the switches - ignition and or kill switch - activate the relay and send 12v direct to the coils. Gets rid of the voltage drop through old switchgear.I've done that for the headlights on the R1. There was almost a 2 volt drop from the battery to the headlight relays. There is now 13.7 V at the bulb holders - I can actually see where I'm going at night!

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[sidecar bob]

I have to ask, did you use a voltmeter or ohms meter at any point during this diagnosis & repair?

[jellywrestler]

those blue connectors are for 2.5mm cable, red for 1.5, mistake right there. it's the old story, most electrical faults are mechanical faults.

[Dak S83]

I have to ask, did you use a voltmeter or ohms meter at any point during this diagnosis & repair?

Yea mate, I have 3 of the buggers, thats the wierd thing though you see, everything checked out, there was little resistance between the kill switch terminals, voltage shown at the igniter and coils was only down about .4 of a volt compared to actual battery voltage which I put down to wiring loom resistances, the only real wierd one which got me on track was the big voltage drop to the coils and igniter while cranking which put me on the track that the starter was stuffed, which it isn't, drawing to much current but, buggered if I know, it seems the kill switch clean did the trick. As long as it stays that way when I get the carbs back and assemble it all again.

[Dak S83]

Ahh, thats a bit better than the previous abortion. Now there is no resistance at all from the positive terminal all the way to the igniter, same with the earth. Just gotta get the carbs back now, they weren't ready for the weekend damn it.