The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: Julio A. on August 20, 2018, 10:03:25 AM
-
Help! I'm getting really confused with all the talk about Ignition Coil and Ignition lead resistance. My coil just conked out and upon checking, it was a weird generic Japanese coil with no usable marking whatsoever.
I'm looking for a suitable replacement but upon doing a quick google search, it seems that there were multiple coil and ignition lead resistances that must be matched unless I risk breaking something in the ignition system.
AFAIK and have read, I'll need a 0.7 Ohm Coil with a 5K Ohm wire. Can someone confirm if this is correct?
Also, any Idea what will happen if I use a lower resistance wire on an aftermarket 0.7 Ohm Dyna Coil?
-
In general the correct Dyna coil is a nice replacement for the OEM part. Determining which Dyna coil to get is beyond me, though.
-
Help!
AFAIK and have read, I'll need a 0.7 Ohm Coil with a 5K Ohm wire. Can someone confirm if this is correct?
Also, any Idea what will happen if I use a lower resistance wire on an aftermarket 0.7 Ohm Dyna Coil?
From SnowBum's site:
The stock electronic ignition bikes (1981+) MUST have 5000 ohm, often just called 5K caps. If the actual value was much lower than 2500, the ignition can be long-term damaged.
I looked for a definitive sentence concerning coils but couldn't find one as clear as above.
-
The ignition coil primary resistance and spark plug lead/cap resistance are two entirely different things and not related in that changing the resistance value of one doesn't really impact on the other.
First the coil. With electronic ignition on an 81 model any dual output coil with a primary resistance of 1.5 ohms will be fine. It could be a dyna or any other after market coil that you can fit with a suitable bracket.
The spark plug leads should ideally be solid copper cored with essentially zero resistance. The spark plug cap should have 5000 ohms resistance to protect the electronic ignition system. Most people will use NGK LB05F caps
-
If you have the electronic bean can use a 1.5 ohm coil with 5K caps
You can use a .7 ohm if you have the correct ignition module. But some have used the .7 with early ign mod with no ill effects
But I see no reason to use the lower .7 ohm coil
you only draw more current and you will not be able tell a difference in the way it runs
If you have a points can use a 3.0 ohm coil with 1K caps
I use the 3 ohm coil (with 5K caps) because i have ran all three with the electronic bean can and couldn't tell the difference
-
Hello
If you have to buy a coil, go at any car junk park and ask for a dual output coil from a European petrol car.
you will get the proper input resistance for a modern electronic ignition (between 0.5 and 1.5 Ohm) and enough juice on the secondary to light up a storm ;-) (I got mine for free as they seldom sell one)
Buy either the BMW plug wires and caps or the NGK 5K Ohm caps and make your own wire and you'll be good.
I would go for the BMW made wires because I ran trough a bad lot of NGK plug caps (4 of them destroyed in less than 10k km...)
but YMMV ....