Ignition Light Problem

edited September 2014 in TECHNICAL
Now that I have a nice new rebuilt engine courtesy of Sir Alf I now have a new problem. The ignition light does not go out. I have checked the connections to the Dynastarter and the coil and can't see anything wrong there. It may be the regulator. The book says that cable 61 may be grounded, but having checked that I can't see it. I do have a spare regulator and will change it over to prove / disprove that theory. Does anyone have any other bright ideas where to look ?  The light doesn't change if the engine revs, but does go out during initial starting. Help please?

Nigel of York


  • edited September 2014
    Hi Nigel,

    Once you have replaced the regulator and have no joy, the next place to look would be the Dynastart brushes. The problem is that you have basically two different systems in one unit. Supplying power to the unit will more than likely make it turn as a motor - proved by the fact the engine will probably turn over (and start - we hope).
    Once it is turning, it requires all FOUR brushes to be touching the commutator. Very common for brushes to wear unevenly, stick in the holders, springs to touch metal when they shouldn't etc.

    Also make sure you are getting a proper earth from the Dynastart to the chassis.

    You can buy a new electronic regulator if you think either / or / both of yours are suspect - they are not cheap, but I can vouch that they work! They can even be hidden inside the original regulator box so no one will know unless you tell them....

  • Thanks john, i thought that might be one possible source of the problem. And i am aware of the company who make the regulators you mention. And yes it does stsrt, and run very well.
  • So here is an update. Dynastart - brushes changed, half worn but were probably ok. Regulator - changed. Guess what - the igntion light is still on. No amount of reving makes any difference. What next ?? There can,t be much else to change. Anybody got any more ideas please?
  • Obvious one that can be overlooked, check the bulb is the correct wattage.

    Next thing would be to trace the wiring and make sure all joints are clean and tight.
    As you take a joint off to clean, do a continuity test on last section of wiring each time. 

    Check the earth from the Dynastart to the engine, Engine to bodywork and then platform to front cowl as there is a sealant line between the two, it relies on the bolts to provide the earth line. Then check the earth behind the dash (if you can find it)

    The other thing is to use a multi meter and do some checking on the output from the Dynastart to the voltage regulator - even though you have changed it, the new one might not be working correctly. If I remember correctly, the repair manual has some test voltages for various output points.

    Also increase the rev's slowly, If your commutator is out of round then the brushes will follow it at low speeds and give output, but at high speed might not have time to come back down from the high point and so be skipping segments (a bit like valve bounce)!

  • Thanks to Sir John of Darn Sarf for identifying that it was my Dynastart that was faulty. Replaced with a spare and now the little red light responds very nicely to engine speed. At tickover, which is a little low, it just glows dimly and soon disappears when the revs increase. So for those of you absent members, you really should try to get to a club meeting. The help and advice from the Club Wizards is free and willingly given, it might just be what you need to get your beast back on its legs.
  • Glad you got it sorted. Sounds like you have the tick over set correctly now. Just remember it will change as the engine loosens up and as it gets warm. So there will always be a compromise on how low to make it when it is cold.

    Too low and it will cough and splutter as you put your foot down, too high and you are wasting fuel.

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