Topic: Just purchased 75 CB750 coil question

[lfalla]

Hello everyone. I just recently purchased a 75 cb750 which has issues with one of the coil wires(#3). It has the stock coils with NGK caps. The cap for # 3 came off the wire. I cleaned out the inside of the cap. Every time I try and screw the cap in the inside of the wire crumbles. Now it is too short.  Not the center wire but the material in between the center wire and the outside sheathing. I had also planned on changing the points over to the Dyna ignition.

I have a pair of NOS honda coils and caps and a set of the Dyna 3 ohm coils that I need to decide between to install with the dyna ignition.
I know this topic has been discussed a lot but I didn't really see a consensus.

I will be keeping the bike completely stock except for the Dyna ignition.

My question is will the stock cb750 see a benefit or a noticeable difference by using the dyna 3ohm coils over a set of new honda coils with the Dyna ignition. If so how is this difference noticed?
I know it will be a stronger spark but can a stock cb750 take advantage of that.
I guess one analogy and probably not a good one would be is it like putting race fuel in a yugo. Not that a cb750 is anything like a yugo because it is a pisser to ride.
I've seen posts where people have had issues with the Dyna 3ohm coils and stock charging system and some that are totally fine. The last thing I want to do is cause more issues,
Your opinions are greatly appreciated.
Thanks,
Luis

[samm_j2]

I have a dyna ignition and thought about running the 3 ohm coils. I also read about how it can tax the charging system... I opted for the 5 ohm coils and things have been great. I don't have any experience with the 3 ohm so can not comment on that.

[lfalla]

I have a dyna ignition and thought about running the 3 ohm coils. I also read about how it can tax the charging system... I opted for the 5 ohm coils and things have been great. I don't have any experience with the 3 ohm so can not comment on that.

Thanks for responding. Did you notice a big difference from stock on the coils or did you do both the ignition and coils at the same time?

[HondaMan]

Something to remember about these engines: they need 4500 volts of spark to fire, no more. What makes them run better is a longer DURATION spark, not a "hotter" one like is obtained from 3-ohm coils. The tradeoff for 3-ohm coils is: while they make more peak voltage, they trade off the duration to get it. The typical 3-ohm coils' spark duration is less than 60% of the OEM coils' duration, and the engines run like it is too short. Those who rave about "it runs better with the new coils" didn't first discover that their old coils were bad, or the plug caps were, before installing the new coils. I have YET to see one of these bikes run better with 3-ohm coils than the OEM coils or the 5-ohm coils from Dyna, provided the plug caps and plugs were good to start with.

I roadracing, when I did it in the 1970s, we used resistor plugs and/or higher-resistance plug caps to stretch out the spark a little longer. It worked: the midget cars that ran 12k-14k RPM on a regular basis with the SOHC4 750 engines used 10k resistor caps over Champion's resistor plugs.