SQ4 Mk2 starting issues

[Paul_Linden]

Bernie, I too have fitted electronic ignition to my Square Four as a Powerspark distributor. You need to choose the correct polarity for your bike and clockwise rotation when viewed from above. The drive gear that Powerspark supply with the distributor will not work on any mark of square four and needs to be changed for the right one. It’s a straight swap and no machining is needed.
Be aware that the auto-advance on the Powerspark distributor is mechanical, and very similar to a Lucas one, but as it is made for an Austin it has a max of about 10 degrees, not the 18 degrees on a square four auto advance. You will need to find a way around that.

[Gui.dorey]

Bernie, I don’t know, but it all seems too complicated for me. I’m not trying to sell anything, but have you looked at Thorspark ignition? They have ready made kits to fit straight into the Sq4, either 6V or 12V. Anyway, I am using one of their kits which was extremely easy to fit and set up, and am very happy with it. Easy starting and the bike runs well.

[berniejones]

I hadn't realised that the Powerspark system used a mechanical advance/retard, I was hoping to go solid state but not sure that's an option unless I make other changes to the electrical system.

I've now emailed Thorspark for some more details. Their web site is a bit odd - it suggests that they only supply kits for magneto ignition but the online shop shows a picture of a distributor for the SQ4 but with no details at all about the system that they actually sell. Hopefully I'll get a response from them soon and can go through all the options again.

Cheers,
Bernie

[Paul_Linden]

About nine months ago I was investigating the merits of both systems (Powerspark and Thorspark) and there really isn’t much technical info on the thorspark site about their system. From what I remember the thorspark has a trigger that fits over the cam and a pick up that does what the points do. I don’t know how it handles the advance.

[berniejones]

So, I now know that both use mechanical advance retard, Thorspark the original and Powerspark a replacement system.

I'm surprised that Powerspark don't go the electronic route as I would have thought that cheaper and easier than building a new mechanical system into a modern replacement distributor - and presumably easier to program a variety of advance curves for different engines.

So, my current shortlist is Powerspark with reduced advance and so time for a 'best-fit' or Thorspark plus a new set of springs for my original distributor.

Both about the same price.

[Paul_Linden]

I bought the powerspark distributor and adapted the advance/retard unit to open to 18 degrees fully advanced. It was possible to do this by comparing it with the unit on my other square four. It’s all working fine I’m pleased to say.
Obviously if you have an original square four advance unit, that would be the way to go, assuming it fits on the Powerspark distributor.
When you get to do the ignition timing on the powerspark distributor they recommend using a strobe, but that’s not an option on a square four. The way to do it is have number 1 cylinder at the right amount BTDC, and with a multimeter in series on one of the leads to the distributor, and turn the unclamped distributor manually until you see the current spike which is the ‘signal’ to the coil. Obviously the rotor arm should be pointing to the number 1 HT lead in the distributor cap.

[berniejones]

It was possible to do this by comparing it with the unit on my other square four

Touch of class there Paul

My distributor is complete and original but there is wear. When I got the bike is was a complete wreck and I was relieved that things like the distributor, generator and drive mechanisms were all there but gummed solid.

I've just ordered a pair of replacement A/R springs from Distributor Doctor so maybe the way to go is to fit those and see how much of the slack that takes out of the system. It may be that makes a sufficient difference for me to then continue to run with the original.

Is the consensus that an EI replacement gives a significant improvement even over a well set up distributor in good condition?

Thanks again,
Bernie

[Paul_Linden]

It sounds like you are heading in the right direction, Bernie.
The ignition system on my square four with the powerspark is working very well. I went for a Lucas gold ignition coil, silicon HT leads, and the bike is 12 volt. I have only ridden in dry weather so I don’t know how waterproof it is.

[paul.jameson]

Bernie,
You are where I was a couple of months ago. I had rebuilt my distributor with new springs but the operation wasn't as smooth as I would have liked. I was already going electronic ignition because all my Sq 4 experience tells me this is the way to go. ( That experience is upwards of 50,000 Sq 4 miles, incidentally.) The new distributor from Powerspark solved the wear problems but despite advice from Paul Linden, I could not time my system either with a bulb or a voltmeter. Powerspark were able to replicate the problem I had and went to some trouble to find me a static timing mark which I have used successfully.

My view is that if you can time your bike with a strobe light - as I think you said you can - then your best option by far will be a new Powerspark distributor.

[Paul_Linden]

I own a small sheet of plastic called a “magne-view film” which changes colour in the presence of a magnetic field. It changes from green to black depending on the direction of the magnetic field it is in. The first picture below is from the website I bought it from, and describes it in more detail. The second picture below is my distributor coming up to firing on number three. The third picture is with magneview film showing where One of the magnets is in the rotor part, before it rotates a bit further and triggers the sensor. Using this method, I got the ignition timing close enough to start the engine (later the timing was set more accurately with a multimeter, as described earlier in this post).