CB750 scrambler project
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Wasted spark is when they both spark at top dead centre?
Have you not gotten any old coil off of another bike? Even a single one that you can get to spark? It would at least prove the rest of the circuit was on par...wrote on 22 Jun 2020, 17:00 last edited by@SpookDog yes wasted spark system is that.
I've ordered new coils as the primary has 3 ohms which is fine but secondary resistance has no resistance at all. On both. This is 1 fault. I'll have to see if there is others.
They are very old and probably corroded inside -
wrote on 23 Jun 2020, 10:23 last edited by
This is the confusion I have , electrics are not my strongest point.
The manual says the yellow/blue wire goes at the top connector on both coils...
The coils are not handed so the green terminal is at the top on one side and black at the bottom when installed.
That's a what's confusing me
I'm still waiting for the new plug caps to try.I'm also not sure if I need to loop the sidestand indicator light as I removed it... I'm pretty sure it just piggybacks
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wrote on 23 Jun 2020, 10:48 last edited by
If it’s connected to the ignition it could be the cause of your problem, specially if you’re neutral lights not working...
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If it’s connected to the ignition it could be the cause of your problem, specially if you’re neutral lights not working...
wrote on 23 Jun 2020, 10:55 last edited byDo you think that's the problem looking at this?
To me it looks like if the neutral light is on (which it is) it should start.
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wrote on 23 Jun 2020, 10:59 last edited by
So it looks like according to the diagram that the G/W wire needs to be tied to Earth if you want to bypass the side stand switch. The Y/Bl wire can just be taped up. I.E. don't complete the circuit for that.
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So it looks like according to the diagram that the G/W wire needs to be tied to Earth if you want to bypass the side stand switch. The Y/Bl wire can just be taped up. I.E. don't complete the circuit for that.
wrote on 23 Jun 2020, 11:01 last edited by@Calum I have the sidestand switch, all plugged in. Only the indicator light isn't connected. Does that affect it? Cheers.
Also still confused on the wires to the green or black connectors on the coils.
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wrote on 23 Jun 2020, 11:29 last edited by
The light only needs to be there if the side stand is down by the looks of it.
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wrote on 23 Jun 2020, 11:43 last edited by
@Calum that's what I'm thinking but if in neutral then it shouldn't Matter ,?
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wrote on 23 Jun 2020, 16:46 last edited by
I can’t get my head round the diagram at the mo. There are a lot of differences from what I know. What about the diode (number 7) condition?
I know that the live wires on the coils will only affect spark timing if wrong, they should still spark. So I’m guessing that the problem is with the side stand, neutral, cutout circuit somewhere, if there’s no spark still...
Sorry I can’t be more help at the mo’. Too many brewskies!🤪 -
I can’t get my head round the diagram at the mo. There are a lot of differences from what I know. What about the diode (number 7) condition?
I know that the live wires on the coils will only affect spark timing if wrong, they should still spark. So I’m guessing that the problem is with the side stand, neutral, cutout circuit somewhere, if there’s no spark still...
Sorry I can’t be more help at the mo’. Too many brewskies!🤪wrote on 23 Jun 2020, 16:49 last edited by@SpookDog yes it's a crappy diagram, I assume the second bulb is the neutral one.
I've never had a diode go wrong on anything but might test it.
I think it's the side stand ... I'll do more tests when the plug caps come.Thanks
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I can’t get my head round the diagram at the mo. There are a lot of differences from what I know. What about the diode (number 7) condition?
I know that the live wires on the coils will only affect spark timing if wrong, they should still spark. So I’m guessing that the problem is with the side stand, neutral, cutout circuit somewhere, if there’s no spark still...
Sorry I can’t be more help at the mo’. Too many brewskies!🤪wrote on 23 Jun 2020, 17:14 last edited by@SpookDog I think if I try to crank the engine over (on the starter motor) in gear but with the clutch switch pulled in... That would also prove if the silicon diode is faulty
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wrote on 24 Jun 2020, 10:06 last edited by
A diode only lets electric pass one way I think. I’d try a continuity/bulb test
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wrote on 24 Jun 2020, 11:26 last edited by
Yeah, it should only show continuity one way. Do a quick google for diode testing...
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wrote on 24 Jun 2020, 11:39 last edited by
@SpookDog thanks.. I tested the resistance and compared it to my spare one, seemed fine. I'm pretty sure it's the sidestand circuit....
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wrote on 24 Jun 2020, 12:32 last edited by
I recon it is as well. I’d connect the side stand and clutch switch stuff all up, put it in neutral and try it with the clutch pulled in.
With the coil connectors, I’d try one ‘one way’ and the other the ‘other way’ if that makes sense? One of them should spark. Once they are sparking it’s easy to figure out which is the outer banks and which is inner...
Good luck my amigo! -
wrote on 24 Jun 2020, 12:37 last edited by
a Diode is like a one way valve for electric. The live wire on the anode and earth on the cathode should have continuity (power flowing through). Reverse the wires and there should be none.
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wrote on 24 Jun 2020, 12:45 last edited by
One other thing! Are the coils making a good earth to the frame? I don’t mean the black &white killswitch wires. I mean where the metal bolts to the frame...
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I recon it is as well. I’d connect the side stand and clutch switch stuff all up, put it in neutral and try it with the clutch pulled in.
With the coil connectors, I’d try one ‘one way’ and the other the ‘other way’ if that makes sense? One of them should spark. Once they are sparking it’s easy to figure out which is the outer banks and which is inner...
Good luck my amigo!wrote on 24 Jun 2020, 12:46 last edited by@SpookDog pulling my hair out,
All the diode does looking at the diagram is. When the stand is down and the bike is in gear, it won't start unless the clutch is pulled in .... But surely is shouldn't allow the starter motor to operate as that alone can knock the bike off the stand,Also should the side stand light only come on when stand is down ( in gear )or all the time including neutral
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wrote on 24 Jun 2020, 12:50 last edited by
I don’t think it’d affect the starter. I think it’s just to stop you pulling away.
I recon it should be on as long as the stand is down.
How many fuses are there as well!
Wish I was there to help. It’s difficult trying to diagnose hands off!... -
wrote on 24 Jun 2020, 13:08 last edited by
Trouble is it could be any one of these switches:
Key Ignition
Handlebar kill
Sidestand
Clutch
NeutralOr these parts:
Pulse generator/pickup
FusesOr just a break in a wire.
I’d start off by checking fuses, then doing continuity checks on the switches, then the wires
Check for volts at the coloured coil wires, volts at pick up while cranking the starter
