MG5 Dynastart electric starter.

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  • #30191
    silverfoxfintry
    Participant

    I am still having problems getting my MG5 to start reliably.
    I thought I had it sorted, but I went to use it earlier in the week, it just won’t start.
    I have changed the fuel, I have changed the plug, I have tried everything!
    It fires, but just won’t keep running.
    I seem to remember someone fitting a Dynastart to a MG5 and I am sure I have seen pictures somewhere.
    And advise, or help is much appreciated.

    Regards

    Iain.

    Attachments:
    #30194
    andyfrost
    Participant

    Are you 100% CERTAIN that your magneto is all correct

    Andy.

    #30196
    silverfoxfintry
    Participant

    Well, when I rebuilt the Engine I set the timing as per the instruction book. Everything is tight and I have no reason to suspect that it has changed.
    However I am prepared to try anything as it is no use as it is.
    The annoying thing is, sometimes I can start it on the first attempt. It then runs well with plenty of power, no backfiring or stuttering.
    I will check the timing again, also the points and the condenser.
    It might be a worthwhile exercise to fit a set of timing marks to the flywheel.

    #30200
    trusty220
    Keymaster

    I had a case like this some years back with a Trusty. It had a Wico A magneto and you could wind it over on the starting handle and get a series of bangs out of the exhaust every time it fired, but it would not carry on and start. Every now and again it would start up and run sweetly, then back to “bang, bang, bang” on the starting handle when you tried to start it next time.

    The problem was traced to the coil just starting to break down internally; I tried a friend’s magneto on it at a ploughing match just to rule it out and to my surprise it ran beautifully, then back to the same old “bang, bang, bang” when I replaced my own one.

    Try to get hold of a proven spare magneto, or otherwise you could take yours off and run it on the bench with a drill with a socket on the drive shaft nut to test the spark.

    I hope that helps.

    #30202
    expeatfarmer
    Participant

    Iain
    I have had a similar problem in the past which turned out to be a magneto fault, just not enough oomph to fire twice. I also have a dynostart fitted to an MG5/6 engine which works a treat I fitted a pulley to the back of the flywheel and mounted the dyno on top of the gearbox. It would be a better job to machine a vee belt groove in the actual flywheel. The other device I have is a two stroke power drill with a 1/2″ chuck into which I have fitted a modified MG starter dog. It struggles a bit on the first compression on my better engines and then turns them over at a fair rate until the engine starts. This enables me to have one starter for multiple tractors.

    #30216
    silverfoxfintry
    Participant

    I have removed the Magnito and reset the points and ran it with a drill.
    I have a spark, but not as fat as I would like.
    Reset the points to 0.015″ and tested again. No change.
    But I did notice that the impulse mechanism was reluctant to trigger. It appears to jam against the post and requires considerable force to make it fire.
    Is this normal? I seem to recall that it was easier when I refitted it to the engine.
    One other thing, the capacitor has a Brass outer casing! I have only ever seen alluminium. Can it be original?
    I am starting to think that a change of Magnito might be worth a try.

    #30218
    ransomes256
    Participant

    Iain,
    Brass cased condenser is an early original and would now be a black plastic moulded item.
    If the magneto is slow to charge / discharge it will spark at start but may not give a constant output when running.
    I have never seen an aluminium cased condenser in a Wico A magneto unless highly modified by a previous owner.
    Neil

    #30219
    silverfoxfintry
    Participant

    Sorry Niel I was not clear. This is the only Wico A Magnito I have worked with.
    On other engines using contact breakers the condensers all had Alluminium casings.
    Are replacements available? Also new points.
    Or am I better just getting the entire thing reconditioned?

    #30220
    charlie
    Keymaster

    Spare parts are available. A quick google search turned up this one amongst others Wico magneto spares Others are listed if you search.

    #30221
    ransomes256
    Participant

    Iain,
    Yes I can supply points and condensers.
    Drop me an email
    Neil

    #30222
    expeatfarmer
    Participant

    When you have the new points and condenser fitted try turning the mag at low speed with your drill and check that the impulse mechanism is working.It should disconnect once you speed up the rotation to about 700/800 rpm After refitting set up a strobe timing light and mark the flywheel at tdc check that spark fires at tdc for starting, if the engine starts and runs it should self advance to 20 degrees. It may be that your impulse mechanism is sticking and retarding the ignition too far to start.

    #30270
    trusty220
    Keymaster

    I was checking my magneto this afternoon and thought that I’d take some pictures just to show you the set-up. You don’t need anything special. I clamped the mag to the bench (I normally use a piece of wood under the clamp to save damaging the cap, but you wouldn’t see the spark if I’d used it), then screwed a piece of rigid wire to the HT lead connector- I’ve straightened out a paper clip before now. Point the loose end of the wire at one of the screws that hold the cap down to the body, put a rubber band around the finger on the impulse starter to keep it retracted, then spin the mag using a variable speed drill fitted with a 3/4″ AF socket. You can buy socket adapters for less than a fiver from Screwfix which work really well.

    You should see quite a spark from the end of the wire if everything is working properly, and this one reached nearly to 1/2″ long this afternoon.

    Attachments:
    #30279
    silverfoxfintry
    Participant

    Well, I have completed a strip and rebuild of the Magnito. I have a good spark, 10mm as per Trusty220’s method.
    However, I am a bit confused about the spark advance.
    I have found no evidence of bob weights to advance the spark.
    Can someone shine a light into my darkness.

    #30280
    ransomes256
    Participant

    Iain,
    There are no bob weights.
    When you rotate the rotor in the corect direction with the magneto mounted vertical the dog in the drive mechanism should drop out and contact the pin in the mounting flange. This then stops the rotor but allows the drive to continue to wind up against the spring. At a further 20 degrees of rotation the drive device contacts the dog and pushes it in and the spring is then released to flick the rotor. ie 20 degree retard to aid starting. Once running the dog is held out of the way by inertia so affectively advancing the spark 20 degrees.
    Hope this helps.
    Neil

    #30290
    silverfoxfintry
    Participant

    I fitted the Magnito today. I have a “fat” spark. I have removed the cylinder head and set the timing to TDC.
    FlusHed the fuel system and refilled with fresh Petrol.
    It s still will not start!
    The best I managed was Bang,Bang!
    I am running out of ideas.

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