Left hand switch gremlins

Z

Zakredridge

Junior member
Location
United Kingdom
Hi
I am having no end of trouble getting my 1200 Laverda to run properly.
Initially it ran great for 25 miles, started to get very warm, and create a smokey haze at the petrol station I had stopped in to check the machine out.
I managed to get home, with a mis fire.
The bike was parked as it had just been rebuilt, (fed up )I was rather concerned at the outcome after spending lots of time and money on this project.
With the smoke/ haze I was convinced I had had a seizure of some kind.
Checked cylinder head, no signs of anything untoward, plenty of oil around the camshafts.
Then I noticed on checking torque on camshafts the rear centre short stud would not torque up, it's thread was stripped.
Realised engine will have to come out.
Engine out, head repaired, barrels off pistons ok.
So I'm thinking what's happening, no mechanical issues to be seen.
Upon checking the battery it was completely dry, I topped up with deionised water and charged her up.
Bike would start but mis fired.
DMC ignition 32.
Diagnosed battery fault, new motobatt and was running a lot better.
New RR, battery failed, bike just stopped.
Another new battery, and I have this mis fire .
Bike won't run without light switch connected, found the little grey link wire was shorting out in the on/off switch link up.
Repaired that, bike started of then starts mis firing.
I have tried several Witt systems including a new Opto (single pick up) same issues.
The light switch seems to be like another kill switch. Even with the repaired switch the bike won't run in the lights off position, won't turn over.
Had a new loom on rebuild, new generator charging coils X2 . Tried reverting to an earlier wiring harness, a new 76 jota3c loom two fuse variety, no joy, tried new coils, don't know how many sparkplugs I've purchased.
Any ideas appreciated.
I'm not an electrician as you can probably tell.
 
I once had a cable catched under a nut which caused temporal shortcuts and had issues that the bike sometimes stopped running and seconds later it worked fine again. Took some time to find the root cause…..
 
Oooh theres a lot going on here?.........from the sounds of it you have got something miswired or crossed somewhere along the way and a lack of correct voltage or its pathway is/may or could be creating issues for the ignition system and hence a misfire.

Obviously the left hand switch gear is a clue and a starting point to work back from,and under normal circumstances if that was taken out of the equation ie disconnected should or would the bike run?.......electrical experts please chip in. but i'm guessing it should.

If it should and yours doesn't then it sounds like your ignition wiring is going down the wrong route,does the kill/run switch work on the other switchgear by any chance (just a thought).

You said it had a new loom on rebuild,was this an exact match or copy or oem stock?

Couple of other thoughts from what you have said in your opening,I would suggest confirming there are no mechanical issues first then you can hopefully cross that off the list.
When you do get the bike running check the charging voltage and make sure that is also good,a dry battery suggests overcharging and though you may have already addressed that with a new R&R have you checked the charging output.

Dodgy batteries can always provide weird electrical gremlins into a system.......personally not a fan of Mottobatt

Apart from that,check all the earths and connections as you go.

Good luck
 
I'm feeling some pain here - understandable!! But as mentioned there's quite a bit going on and bound to be some crossover - but smoke from where? engine implies mechanical, not electrical.

No doubt whatsoever that there's a misdirection of voltage going on somewhere, so identifying the source and rectifying that is priority number one. No way should an ignition system require the headlights on to function!! If it were me, I'd be isolating the ignition system and running it directly from the battery to test. Then judicious use a multimeter to trace where your wires are going and working out where they SHOULD go.

Nothing about your issues is unresolvable - in fact I reckon you'll find the solution is fairly straighforward - it's the tracking down that is complicated.
 
piranha-bro2 said:
I'm feeling some pain here - understandable!! But as mentioned there's quite a bit going on and bound to be some crossover - but smoke from where? engine implies mechanical, not electrical.

No doubt whatsoever that there's a misdirection of voltage going on somewhere, so identifying the source and rectifying that is priority number one. No way should an ignition system require the headlights on to function!! If it were me, I'd be isolating the ignition system and running it directly from the battery to test. Then judicious use a multimeter to trace where your wires are going and working out where they SHOULD go.

Nothing about your issues is unresolvable - in fact I reckon you'll find the solution is fairly straighforward - it's the tracking down that is complicated.
Click to expand...
Yes it's perplexing, I have wired the ignition separately on a relay and it still erratic.
 
Regardless of any outcome, fitting that relay is a good move. I think your wiring issues are more about why the LH switch is entering the equation. So if you can run a dedicated power feed wire to operate the ignition and coils with no chance of 'escape' beyond those functions, then test the engine, you can at least remove those items from consideration. There's also the RH switch starter-kill circuits to test and if possible eliminate.
 
The horn button is on the left switch; maybe it's actively powered instead of actively earthed. Big guess on my part. The horn has confused plenty.
 
The theory explained below may be something of a long shot, but in my experience it's worth investigating if only to rule it out as a cause of the problem.

Moto Witt ignitions can be sensitive to high voltage. When my Jota had a Witt ignition, it gradually started to misfire more and more over a few months. But if I switched the headlight on, the misfire would clear and the bike ran OK. So for a while I rode everywhere with the headlight on. Eventually the problem got worse and it would misfire even with the headlight on.

I was pretty sure the ignition unit was the source of the problem, so I contacted Uwe Witt and we had a useful email conversation. He told me that his Moto Witt ignition system was designed to run on 12V, but it won't tolerate much more than that. If the bike's system voltage is too high for the ignition, then it'll misbehave. Switching the headlight on will cause a small voltage depression and the ignition will be happier. Uwe sent me what he called a voltage reducer (presumably just a resistor) to put in the power supply wire to the ignition unit that reduced the voltage it sees to around 10V. That kept it going for another year or so. But eventually, as the ignition unit got older, its threshold "happy" voltage reduced even further. It got so bad that it wouldn't even run with the voltage reducer. I chucked the Witt unit in the bin and fitted an Ignitech ignition. The bike was re-born. It started easily, ran smoothly with no misfire and used less fuel. That was 16 years ago and the ignition is still working perfectly.

It may be that your Witt unit is also not in its happy place in relation to voltage. If that's the case, there could be two causes:
1. Your voltage regulator is running the system at a higher than usual voltage (should peak at around 14V when you rev the engine)
2. Your Witt ignition is on a deteriorating voltage tolerance curve like mine was.

To test the above theory, try putting a resistor in series with the Witt ignition box to reduce the voltage it sees.

I'm not sure what the resistance value was of the "voltage reducer" that Uwe sent me (all that stuff went in the bin with the old Witt ignition), but I'd guess that the ignition box probably draws around 2 Amps, so its internal resistance would be about 6 Ohms. Any external series resistor would need to be a fraction of that. I'd guess 2 Ohms would probably be in the ballpark. There will be a couple of Amps flowing through it so I'd suggest you buy a resistor rated at about 5 Watts just to ensure it doesn't have a melt-down. That'll most likely be a ceramic type. Any electronics store should stock them and it'll only cost a few pence. Disconnect the 12V supply to the Witt box and re-connect it with the resistor in series with the ignition box. If you find it improves matters, the ignition unit may be on its last legs, as mine was.
 
Schurminater said:
Oooh theres a lot going on here?.........from the sounds of it you have got something miswired or crossed somewhere along the way and a lack of correct voltage or its pathway is/may or could be creating issues for the ignition system and hence a misfire.

Obviously the left hand switch gear is a clue and a starting point to work back from,and under normal circumstances if that was taken out of the equation ie disconnected should or would the bike run?.......electrical experts please chip in. but i'm guessing it should.

If it should and yours doesn't then it sounds like your ignition wiring is going down the wrong route,does the kill/run switch work on the other switchgear by any chance (just a thought).

You said it had a new loom on rebuild,was this an exact match or copy or oem stock?

Couple of other thoughts from what you have said in your opening,I would suggest confirming there are no mechanical issues first then you can hopefully cross that off the list.
When you do get the bike running check the charging voltage and make sure that is also good,a dry battery suggests overcharging and though you may have already addressed that with a new R&R have you checked the charging output.

Dodgy batteries can always provide weird electrical gremlins into a system.......personally not a fan of Mottobatt

Apart from that,check all the earths and connections as you go.

Good luck
Click to expand...
Yes the loom was a btz day time running lights loom replica made in the UK, £300.
It initially starts up and sounds great, then the mis-fire starts. Something is pulling voltage down....
 
Dellortoman said:
The theory explained below may be something of a long shot, but in my experience it's worth investigating if only to rule it out as a cause of the problem.

Moto Witt ignitions can be sensitive to high voltage. When my Jota had a Witt ignition, it gradually started to misfire more and more over a few months. But if I switched the headlight on, the misfire would clear and the bike ran OK. So for a while I rode everywhere with the headlight on. Eventually the problem got worse and it would misfire even with the headlight on.

I was pretty sure the ignition unit was the source of the problem, so I contacted Uwe Witt and we had a useful email conversation. He told me that his Moto Witt ignition system was designed to run on 12V, but it won't tolerate much more than that. If the bike's system voltage is too high for the ignition, then it'll misbehave. Switching the headlight on will cause a small voltage depression and the ignition will be happier. Uwe sent me what he called a voltage reducer (presumably just a resistor) to put in the power supply wire to the ignition unit that reduced the voltage it sees to around 10V. That kept it going for another year or so. But eventually, as the ignition unit got older, its threshold "happy" voltage reduced even further. It got so bad that it wouldn't even run with the voltage reducer. I chucked the Witt unit in the bin and fitted an Ignitech ignition. The bike was re-born. It started easily, ran smoothly with no misfire and used less fuel. That was 16 years ago and the ignition is still working perfectly.

It may be that your Witt unit is also not in its happy place in relation to voltage. If that's the case, there could be two causes:
1. Your voltage regulator is running the system at a higher than usual voltage (should peak at around 14V when you rev the engine)
2. Your Witt ignition is on a deteriorating voltage tolerance curve like mine was.

To test the above theory, try putting a resistor in series with the Witt ignition box to reduce the voltage it sees.

I'm not sure what the resistance value was of the "voltage reducer" that Uwe sent me (all that stuff went in the bin with the old Witt ignition), but I'd guess that the ignition box probably draws around 2 Amps, so its internal resistance would be about 6 Ohms. Any external series resistor would need to be a fraction of that. I'd guess 2 Ohms would probably be in the ballpark. There will be a couple of Amps flowing through it so I'd suggest you buy a resistor rated at about 5 Watts just to ensure it doesn't have a melt-down. That'll most likely be a ceramic type. Any electronics store should stock them and it'll only cost a few pence. Disconnect the 12V supply to the Witt box and re-connect it with the resistor in series with the ignition box. If you find it improves matters, the ignition unit may be on its last legs, as mine was.
Click to expand...
I've read of your experience on my path for knowledge, it may be a consideration for the older witts, but my brand new one, single pick up it is still occuring.
But if I do that it will rule it out at least?
 
I remember years ago when I rebuilt my first Z1 it was fitted with a Boyer ignition and at some point of testing the electrics and with no plug caps fitted every time I put the indicators on I would get a constant stream of electricity pouring out of every HT lead it was like the birth of Frankenstein and I couldn't figure it out.
In the end it turned out to be as simple as low battery voltage,the ignition system would charge at say 10 Volts but if the voltage went below 9 Volts it would discharge and putting the indicators on created the perfect charge /recharge scenario.
 
Zakredridge said:
I've read of your experience on my path for knowledge, it may be a consideration for the older witts, but my brand new one, single pick up it is still occuring.
But if I do that it will rule it out at least?
Click to expand...
I have the same unit as yours and when the RR starting putting out a high voltage with the side lights on and ignition was far from happy. From memory it was something like 17volts, new RR sorted it.
 
Zakredridge said:
I've read of your experience on my path for knowledge, it may be a consideration for the older witts, but my brand new one, single pick up it is still occuring.
But if I do that it will rule it out at least?
Click to expand...
Probably.

Sorry, I know that's not very helpful. But it's hard to be 100% confident of anything when diagnosing an electrical fault via the forum. If I had the bike in front of me and could probe at its electrical system I'd be more positive (pun intended).

If putting a resistor in series with the Witt unit makes it behave better, all that tells you is that the Witt prefers a lower voltage than it's getting. A brand new DMC is unlikely to be suffering from age-related decay like mine was, so the scenario may be that your RR is putting out too high a voltage. The fix for that is either to experiment with different values of series resistor to get it running sweet throughout the rev range or to try another RR.
 
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