Mark wrote: Interesting stuff have just gone through those checks ohttp://www.kz1300.com/index.php/forum/welcome-mat/1838-testing-coils/reply/12742?quote=1#n the original coils with the fixed HT leads. BUT what if the coils are 3 ohm coils that a lot of us have upgraded to what readings would be expected then across the secondary windings I notice a big difference when checking albeit consistent, original coils are averaging 14 ohms, upgrades 11.5 Ohms. which is below the manual reccomendations
Aftermarket ignition coils fall in to a category I like to call "Black Art". One of the first upgrades people want to do to hype up their bike is upgrade the ignition coils to get a hotter spark. Coil manufacturers prey on those who want the hotter spark and then they go and make a product which"guarantees" a hotter spark in an attempt to sell their product. There's a lot of engineering that goes in to the electronic design of an ignition coil and I'm not the guy to post that type of information. I'd leave that up to Trikebldr because he has a much stronger background understanding of this topic than I.
So just some fundamental basics here. We have primary windings and secondary windings in a coil. The primary winding will have a certain number of turns let's call it X and the secondary winding will have a certain number of turns let's call them Y. The output voltage of a coil will equal the input voltage times the secondary windings divided by the primary windings. So if the input voltage was 10 volts and there was 1 primary winding and the secondary winding was 10 windings, then 10 volts times Y divided by X = the output voltage 100 volts.
So back to the question. The primary winding could be any number of turns and the secondary winding could be any number of turns. The diameter of the wire in each of the windings can be any diameter. The resistance of the wire in each of the windings is dependent on the length of the wire and the diameter of the wire. Based on all of the variables I've identified here. The question of what you'd expect to see when testing your aftermarket coils - the only place to look for the proper resistance would be specs as laid out by the manufacturer of the coil, not the specs as listed in the shop manual.
Trikebldr had a very interesting post on this topic about a year ago delving into the theory of the coils and ran into some health issues and didn't finish the "lesson" There's a lot to this topic and what I've just posted is about as basic as kindergarden electronics but it's enough to try to help explain or give an answer to the question asked here. We'd be blessed if Trikebldr finished off his post on the subject. It's a fascinating subject for some of us, and a flying lead balloon for others. Ideally, it would be great to just come up with "the ultimate fix" for the coil issues on these machines instead of everybody doing different things.
We always refer to the resistance of the primary windings on our bikes as being the critical number since too low of a resistance and you'll fry the igniter. Too high of a resistance and you'll end up with a weak spark. What's really important is to not draw too many amps on the primary windings since the internals of the igniter can't handle the load. The voltage in the system is system voltage which should be around 14.2 volts as a standard. The resistance is the value based on the resistance of the coil and the other items in the primary circuit. Amperage drawn in a circuit is equal to the voltage of the circuit divided by the resistance of the circuit. Mess with the voltage or the resistance and there will be an effect on the amperage drawn in the circuit.
Hope this helps,
KB
