No, the power loss problem was when I changed the plugs from iridium 7's to normal 7's. I did also change my air filter to a uni foam filter at the same time. Maybe it's the air filter that's making me feel like the bike has no balls. As to my sesitive butt, that thread is in another forum.
I imagine it's the air filter. I'd guess you don't have the stock exhaust either. The 78 carbs were finely tuned (on the lean side) for both the exhaust and air filter restriction characteristics. Open exhaust evacuates the cylinder faster, so there is more oxygen available on the next cycle (needs more fuel). And, the free-er air inlet changes the carb throat vacuum, reducing it, so it pulls less fuel from the carb fuel jets. Both these changes require you rejet the carbs. Most likely bigger mains and raising the slide needle height will wake the engine up.
By the way, why do you think the PO changed to 3ohm coils. I have the 5ohm stock coils in a box that came with the bike. Is it advantageous to have 3ohm vs 5ohms. Should I revert to the 5ohm, and if I do, what differences will I notice apart from the draining issues being solved?
The PO may have been told (and believed) that more spark meant more HP. The 3 ohm coils can make more spark if the spark gap is increased. And it will make more spark at lower input voltages than the stock ones (like during electric start when the battery voltage sags). Could also be that a 750 centric guy advised him, who was used to a bigger charging system. Could be that "modern" meant more to him than a vintage bike.
Could also be that there was an ignition wire problem with the old coils. Whatever the reason, it was the wrong selection for your application, it appears.
If you are using a spark gap of .025-ish on whatever plug you select, I'd go back to the stock coils if the wire leads are undamaged. Or, you could seek out a 750 guy that wants 3 ohm, have him get the 5 ohm versions and swap. Or, maybe Dyna will take yours in trade for 5 ohm if you call them up?
Unless there have been compression changes in your engine, or you require a larger spark gap, you won't notice much difference in the way the bike runs, after you get the battery back up to full charge, of course. If your battery is weak, or there is voltage drop between battery and coils, then starting might be more difficult with 5 ohm coils. But, I advocate fixing those issues rather than drain the battery with fat coils.
Cheers,
