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Timing Pazon ignition on a Dommie

Submitted by tony_wood on Sat, 22/08/2020
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Heavy Twins

Hi. Has anyone out there fitted a Pazon Surefire Ignition system to a Dommie 99? (Mine’s a 1960). I’ve looked at the Pazon instruction booklet and it seems to suggest setting the timing at 31 degrees before top dead centre rather than 28 degrees BTDC (is that the  ‘factory standard’ Dommie setting?). I was wondering what other people with Pazon ignitions on Dommies have done regarding the timing setting. I know that I could contact Pazon but I thought I’d try and find some real-world experience from other owners, if there’s any out there.

I’m also interested to know why there’s a 3 degree difference between the  ‘standard’ BTDC setting and the Pazon recommended one - does that 31 degree setting not risk pinking?

Thanks

Regards

Tony

Submitted by robert_tuck on Sat, 22/08/2020

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As a guess,I thnk the Pazon has a slower advance curve than the std Norton and the extra bit of advance  offsets this.  One of the  down sides of the earlier Boyers was the later advance and the Pazon people  are well aware of this . Just my theory.

Submitted by tony_wood on Tue, 25/08/2020

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I also contacted Pazon to seek their advice (extremely helpful and very quick in answering!). Here’s the reply I got from them:

The 31° timing figure was arrived at many years ago (decades, in fact), after much testing with electronic ignition systems by the Norton factory.

With electronic ignition it was found that, due to the more progressive advance curve (i.e. full advance not being reached until higher engine rpm), the full advance could be increased from the standard 28° to 31° BTDC.

However, you can set it to anywhere between these two figures, depending on your own experience and preferences.

For example, if you are using low octane fuel (which is likely, when compared to the fuel used all those years ago), you may find 28° may suit your engine, rather than 31°

So it looks like there’s quite a broad band (3 degrees) of variation that will be acceptable. I might go for 29.5 degrees just to be on the safe side.

Regards

Tony

 

Submitted by robert_tuck on Tue, 25/08/2020

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My guess was not wrong then!, Our Atlas with early Boyer is timed at around 26degrees  which makes for a soft easy to start woffly  motor  with Commando pistons and a compression plate. It has never kicked back even with a nearly dead battery. I will be going  to 28degrees once run in. Just to see what difference it makes. I suspect that with the slow advance curve and the unlikely event of exceeding 5000 revs we could run at 30 degrees with no issues. I have noticed that one pipe is well blued which is a puzzle with only one carb. Perhaps there is a slight air leak on one side of the manifold.I would doubt that there is a timing varience on the cylinders with the boyer,but will be strobing both sides.

 


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