Dyna Coil

[tunnelrider]

This is not about the fact it's a Dyna coil. Any 3 ohm coil would work with electronic ignition, the fact that it's 3 ohms instead of 1.5 ohms would not stop it working.But you effectively have a points type coil triggered electronically so in terms of spark energy it will be similar to the earlier points ignition system.And points systems on the early R45/65's work just fine so it's no surprise to hear yours runs OK

The question really is what advantage did electronic ignition give over points ignition. The simple answer is electronic ignition will have more in reserve than a points ignition but will not necessarily make the engine run better. There is nothing that you can tell from published power figures.The ignition systems on R45's and R65's were identical so where it's possible to make a direct comparison, the R45 still made 35HP regardless of the type of ignition system. R65's were upped from 45HP to 50 HP for other reasons like larger valves at the same time electronic ignition was introduced so a direct comparison isn't possible but I'm sure there wouldn't have been a difference in power output.

As long as your engine runs well I wouldn't worry but there is a test you could do.The spark plug gap spec is 24 - 28 thou.If you found that the engine ran better with the plugs set at 24 thou than it did at 28 thou then that would indicate that spark energy is a limiting factorand a change to a 1.5 ohm coil would be beneficial.

Thanks very much Barry for your clear and concise reply, it makes a lot of sense.  I'd be very reluctant to start playing with things that ain't broke anyway, but your plug gap test is something I've just learned, thanks.  I can say for sure it makes no difference as I've done slightly different gaps with plug changes and no noticeable difference.  Thanks for the info.

[Barry]

And electronic ignition systems such as Boyer that were designed to replace the points (and advance retard) and leave the rest of the ignition train otherwise untouched.

True, and even the early original electronic ignition systems introduced by Honda had coils of approx 2.8 Ohms which is close enough to a 3 ohm Dyna. All Honda did was replace the points with an electronic switch as like BMW they retained a mechanical advance mechanism. "Electronic ignition" must have been good for marketing but in substance it didn't really amount to much. They just removed the need for maintenance of the points. Which of course was a good thing. I had a 1980 Japanese bike from new and ran it for 12 years without once having to think about the ignition system.

An ignition coil from a late 70's Honda 4's could be used on a points airhead or an electronic ignition airhead for that matter.


Tunnelrider,  

I know I've mentioned this recently in another thread but in case you missed it - For best performance it's important that a coil with an exposed laminated core like a Dyna is properly bolted to the frame or to a mounting bracket in order that the magnet loop is completed.

[tunnelrider]

Barry, it's bolted down good, cheers.