Difference in resistance between coils

Okay - so this is a 'continuation' of the thread I have in the carbs forum, since its obviously taken an electrical turn.

I replaced the plug wires last night, and have a 10ohm difference between the sets of boots. 1&4 showing 12.4K(ish) and 2&3 showing 23.2K(ish).

Does it matter that there is a 10K ohm difference between the pairs? Will the plugs still fire the way they need to? I'm not sure why the 2/3 wires are different, but I've tried everything I can do to clean up the connection.

thx.

I would have to say yes. That is a rather large difference. Do you measure that same difference if you just measure it at the coils with the wires off? If so, you probably have a bad coil. If not, you need to find out wich wire is bad by measuring each one seperately.

Sounds like someone (previous owner?) replaced one coil with a coil for a KZ650 - some (early) 650 coils should read around 23 Kohms on the secondary (between plug caps).

More importantly the 23KOhm coil is for points ignition and should measure around 4 ohms on the primary (between the two small lugs on the front of the coil) - a coil for electronic ignition should only measure 1.8 - 2.7 ohms on the primary side. A 4 ohm coil will work alright with a Dyna ignition but is likely to cause a weak spark with a stock IC igniter. (I´m not really familiar with the 550s, but being an '84 I assume it has electronic ignition?)

Post edited by: OnkelB, at: 2006/10/18 10:33

Yep, it is electronic.

I'm pretty sure that I measured around 18Kohms at with the wires off - though I'll double check that this evening. The 1/4 coil was around 12 with the wires off, right at the terminals.

Is there a part number on the coil itself that I could check to make sure its the right coil for the bike? I'll check bkawi.com to figure out which coil it should be.

What will this do to the bike? Assuming that I can get it started, I figure it will lower my fuel efficiency and performance, right? Anything else? Hope I don't have to look into new coils because of this :pinch:

Post edited by: pyxen, at: 2006/10/18 14:53

I could very well be wrong about the 650 coil, it´s just that the 23Kohms rang a bell - the 23Kohm coils are kinda special as most KZ coils should read between 12-18 Kohms between the plug caps.

There´s a number on top of the coils, start by checking if the number is the same on both coils - also measure the primary resistance, if the primary reading is the same (app. 1.5-2.7 ohms) on both coils my theory is wrong and your problem lies elsewhere.

Got the resistance to read 15K on the 2/3, but its not firing now.

I have the bike started but it revs up and dies.

I've continued the thread in the carb forum, but are there any electrical reasons that the bike would start rev and die?

Thanks for the help

Is the bike firing on all four cylinders now?
If not, then see my post in your carb thread.

nope - not yet..gonna do what you said in the carb thread.