76 cb750 Charging Problems

[rcbronc]

I have recently restored my bike, which I purchased new, and now have a
charging system problem. I have installed a Dyna DS1-2 ignition which probably
has contributed to some of my problems. Anyway this is what I have done/found
up to now:

I started this trouble shooting exercise when I ran my bike after it was rebuilt it would run reasonably
well to start with but within 5-10min. of run time it would start to miss and bark during
increase throttle.
I checked the battery voltage with the bike running and there was no increase in voltage
with rpm, stayed around the 12-12.8vdc.

Bypassed the regulator with no change
Field and stator coil resistance checked out per manual
I then connected a 10A digital meter across the main fuse( fuse removed) to check actual
charging current and this is where my real questions are:

When I turn my ignition on the draw on the battery is >10A
When I started the bike the draw dropped to approx. 9A with no sign of charging.
I was surprised at the large draw on the battery with just the key on so I started pulling loads off and
checking the impact:

1) disconnected the headlight current dropped from >10A to 8.25A
2) disconnected one Dyna ignition coil, supply side, current dropped from 8.25A to 6.22A
3) disconnected the other Dyna coil  and current dropped from 6.22A to 3.98A

I was surprised to see an approx. 2A current draw through each coil with just the ignition switch on.
With the old point system one could see that when one point was closed but not both at the same time..... Anyone have any thoughts on that one.

Also it would be great to know what the typical current draw was on a working bike with the ignition switch on, and motor not running......Anyone??

One more thing to add. During my restoration I installed a 836 kit, cam , and installed a lightened alternater from CycleX, which is basically a stock alternator rotor which has been shaved down to reduce the rolling mass. I am now thinking this would also have an impact on the charging efficency with a smaller rotor??

Any thoughts or suggestions would be greatly appreciated,

Russ
 

[Re-run]

Well one thing, at idle, the sohc engines do not charge. Charging does not start till after 2000 rpm. So start the bike and rev to about 2500 and see what the voltage is.

What ohm rating are your dyna coils? Did you get the 5 ohm or 3 ohm? The 3s will draw more current and drain battery faster is it is not being charged.
The dyna s will start loading the coils with the key on and will drain the battery and possibly overheat the coil if left on for too long as the voltage does not discharge.

[vern401]

 On the subject of coils. Is there a good place to get New OEM grade coils for these bikes?
 I'll be looking for new replacement coils that have the Honda OHM readings and the ability to replace the plug wires if needed.
 I'd like to avoid Ebay if possible.

[Re-run]

Well I have not tried them, but partsnmore.com has coils like the ones we have now for $30 each I think.
While not cheap, they are 5 ohm and should have the right wires with them already and are half the price of new dyna coils. I have been thinking about a coil swap and have been looking at these myself.

https://www.partsnmore.com/cat_index.php?model=cb750_sohc&category=electrical
about 1/4 the way down. Needs plug caps though. If your old ones are still good, you could use those.
They also sell the coils for the dohc which requires wires and is a lower ohm rating but would still work if the charging system is working good.

[vern401]

Good I want to say as close to stock OHMS as I can. The price is not bad for new. There are allot of other parts that are high ware items that they have on there too.
Thanks Again Re-Run

[Re-run]

No prob Vern!