Ignition Woes

[Mahaman]

1981 XS650 Heritage Special
Can't shake out the electrical gemlins. First problem was the charging system. Now sorted after replacing the Rotor, Stator, and Regulator. Word of warning, don't buy the cheap Chinese regulators. I finally settled on an Electrix unit from the UK. Third attempt.
Now, all should be fine, but no. Bike runs fine until I get a temporary ignition cut when I change from low beam to high beam or back. Also temporary ignition cut when the indicators flash.
Common denominator is the left handlebar switch block (new), but checks out ok. Have checked all the ground connections (black wires). Have removed the reserve lighting unit.
Have temporarily removed the sidestand relay so nothing shorts the TCI box. Has new ignition switch. All connections in the headlight checked. Have mounted a voltmeter on the handlebars, and no noticeable dip in voltage.
I put it down to a faulty TCI unit, but before forking for a new one, would be grateful of any suggestions.
Cheers.

 

[Its been a long time]

Relatively inexpensive to try a Gonzo box *. Several members here are running them in place of the stock TCI box. I think one member makes pigtails to ensure using a Gonzo is plug and play. Apologies, I don't remember who makes them. There's threads in the forum about doing the conversion.

* GN250 igniter box.

 

[Mahaman]

Update. Have bought an Ignitech unit. Have used them before. Unfortunately, no different.
Bike runs fine, with indicator and headlight fuses removed. Runs fine with indicator fuse installed, untill they flash. Misses and farts when headlight fuse installed. No hair left now.
Must be bringing the volts down somehow, but can't find it.

 

[MikeyDeepXS]

If the ignition coils seem to be losing juice when the headlight is on, that seems to point to a bad battery and/or charging system.

How old is your battery?

 

[Mahaman]

New battery. Lithium Ion 500CCA.

 

[MikeyDeepXS]

Interesting….

How about your key switch and killswitch? Have the contacts been cleaned recently?

Also, maybe try wiring directly from the main fuse to the ignition coil(for testing purposes) and see if that yields different results.

Voltage drop is dependent upon resistance in the circuit. If you’re measuring voltage directly from the battery with your volt meter, it’s only going to show if the battery voltage drops from a high amperage load. On the other hand, if you have high resistance in those switches, the voltage at the ignition coil could be low to start and get even lower when a heavy load or alternative path gets connected into the circuit.

If you’re 100% sure the battery is good, then it’s sounding a lot like high resistance

You could possibly check this by using an ohm function on a meter and ohming between the + battery terminal and the red wire on the ignition coils

 

[Mahaman]

Thanks for your reply. Ran a wire from the fuse to the coil as you suggested. No change. I hear you, and everything points to a reduced voltage that affects the ignition. Have spent another full day chasing my tail with no solution. The next plan of attack is to replace the coil. All the resistance values checked out ok, but the spark looks weak. The bike starts ok, but I should have done this at the beginning. Will keep you posted.

 

[Mahaman]

Also, Ignitech ignitions will work down to 8V. Nowhere near that. This is a curly one. Determined to not let it best me.

 

[Its been a long time]

You replaced the rotor and stator. Is the rotor an original Yamaha/Hitachi rotor?

 

[Signal]

Did you wire the ignitech from the battery via a relay controlled by the ignition switch circuit?
If not in the running condition the ignitech unit may be getting enough voltage to operate, but in the fault condition with the extra load and voltage drop causes the ignition to see a low voltage dip and reset the ignition causing the temporary engine miss.

Also an ignitech will highlight other weak ignition components, coils, leads ,caps and plugs but i think your problem is elsewhere.

I was looking at electrex world reg /rectifiers earlier this year and could not find one that they had for use with a lithium battery, what one did you get?

 

[Mahaman]

You replaced the rotor and stator. Is the rotor an original Yamaha/Hitachi rotor?

Have replaced both rotor and stator. Stator is chinese, but not sure about the rotor.

 

[Its been a long time]

Have replaced both rotor and stator. Stator is chinese, but not sure about the rotor.

I suggest you check it out. If it's not an original, it's probably Chinese. They're known to have issues with the magnets for the ignition pick ups being inadequate and causing issues. If you post pictures of it here you'll find out what it is. It would help if you said where you bought them from too.

 

[Mahaman]

Bought it from Geoff's XS in Sydney. Part number 24-2652. Pretty sure the pick-up is a reluctor type. ie. No magnets, just metal passing a powered coil.

 

[Its been a long time]

Bought it from Geoff's XS in Sydney. Part number 24-2652. Pretty sure the pick-up is a reluctor type. ie. No magnets, just metal passing a powered coil.

OK. 99% sure it's Chinese then. There's a known issue with TCI stators that aren't OEM. It's related to the magnet embedded as the TCI trigger. It's above my pay grade explaining why. Maybe @Jim who rewinds OEM rotors will explain.

One of these, says it's not a rewind, so it's 99.9% certain to be Chinese.

https://www.geoffsxs.com.au/en-gb?route=product/search&search=24-2652&description=1

To be crystal clear, you're using the OEM TCI pick up, but with aftermarket rotor and stator?

 

[MikeyDeepXS]

One way to diagnose the stator+rotor’s effect on this issue would be to take them out of the equation and see what happens.

On a full battery, The bike should be able to run for several minutes without the charging system working, even with the headlight on. Unplug the regulator and rectifier and see if the problem persists.

I believe @Its been a long time is referring to the aftermarket rotors having issues. The stator connects to the three white wires and sits stationary in the side cover. The rotor rotates with the crank and attaches electrically via sliprings

 

[Its been a long time]

One way to diagnose the stator+rotor’s effect on this issue would be to take them out of the equation and see what happens.

On a full battery, The bike should be able to run for several minutes without the charging system working, even with the headlight on. Unplug the regulator and rectifier and see if the problem persists.

I believe @Its been a long time is referring to the aftermarket rotors having issues. The stator connects to the three white wires and sits stationary in the side cover. The rotor rotates with the crank and attaches electrically via sliprings

If there's a problem with the Chinese rotor trigger magnet, that's not going to help. There's a known issue with Chinese rotors relating to magnetic field and the trigger magnet.

I'm not saying it's definitely the problem here, but there's a known issue with aftermarket rotors.

 

[MikeyDeepXS]

If there's a problem with the Chinese rotor trigger magnet, that's not going to help. There's a known issue with Chinese rotors relating to magnetic field and the trigger magnet.

I'm not saying it's definitely the problem here, but there's a known issue with aftermarket rotors.

Why wouldnt it help?

He said it runs good until the headlight or blinkers turn on… so my thinking is that the added load to the system is causing the issue.

If it’s a problem with the pickup/rotor’s interaction then why wouldn’t it effect the system at all times?

I’m considering that there might be electrical interference happening between the rotor and the pickup under heavy load which triggers the charging system to kick in with more power, which makes it seem plausible that eliminating the charging system from the equation could reveal whether or not it’s at fault.

Is there something I’m missing?

 

[Its been a long time]

Why wouldnt it help?

He said it runs good until the headlight or blinkers turn on… so my thinking is that the added load to the system is causing the issue.

If it’s a problem with the pickup/rotor’s interaction then why wouldn’t it effect the system at all times?

I’m considering that there might be electrical interference happening between the rotor and the pickup under heavy load which triggers the charging system to kick in with more power, which makes it seem plausible that eliminating the charging system from the equation could reveal whether or not it’s at fault.

Is there something I’m missing?

OK I misunderstood slightly. You would run with rotor not energised? That would be an effective test. It would confirm if there's an issue with magnetic field and the TCI magnet. Sorry for not fully understanding first time around.

 

[MikeyDeepXS]

Re-reading the original post it almost leads me to believe that the problem is occurring in the ignitor unit itself due to a transient spike of emf caused by the switching.


I kinda tend to suspect the battery and regulator combo now as the battery does serve the role of noise suppression in the system.

The rotor and regulator are constantly creating noise when working properly, the regulator itself suppresses it along with the battery. The regulator would be constantly switching causing spikes in emf while it’s charging(from my understanding of how it properly works), which kinda makes me scratch my head a bit

 

[MikeyDeepXS]

Via the AI overlord:
How to Fix or Prevent the Interference-

If you want to keep the lithium battery but eliminate the light-switch ignition stumbles, implement these filtering corrections:

1.Add a Capacitor: Wire a large automotive-grade capacitor (e.g., a 25V, 4700µF+ or a dedicated "battery-less" capacitor block) in parallel with the battery terminals. It will act as a secondary hardware filter to absorb transient spikes before they reach the ignition system, even if the BMS momentarily triggers.

2.Upgrade to a MOSFET Regulator: Ensure your solid-state regulator is a modern MOSFET or Lithium-optimized unit (such as those from RM Stator or Oregon Motorcycle Parts). Unlike older shunt or standard transistor regulators, MOSFETs switch cleanly, run cooler, and do not throw the microsecond spikes that trigger lithium BMS safety shutdowns.

3. Isolate Ignition Wiring: Ensure your ignition pick-up/trigger wires are physically routed away from the main charging and headlight wiring harnesses to prevent cross-talk.