How to run a CB77 without a battery?

mike in idaho · Post by **mike in idaho** » Wed Apr 24, 2019 6:19 pm

It wont run,wired like that. The lead from the condenser is to be connected to the same terminal as the wire from the points(marked minus). The plus marked terminal of the coil is connected to a source of 12 volts. You need the stator leads wired to a rectifier to have a source of 12 volts, also you need either a capacitor or a battery in the circuit to adequately charge the coils with enough energy to make a spark.

1204_cb77 · Post by **1204_cb77** » Wed Apr 24, 2019 7:50 pm

mike in idaho wrote:It wont run,wired like that. The lead from the condenser is to be connected to the same terminal as the wire from the points(marked minus). The plus marked terminal of the coil is connected to a source of 12 volts. You need the stator leads wired to a rectifier to have a source of 12 volts, also you need either a capacitor or a battery in the circuit to adequately charge the coils with enough energy to make a spark.

Ok, this makes sense. The condensers more or less absorb excess spark correct? I may swap the two small ones out with one unit with dual leads.

I will most likely pick up a capacitor online, I have seen a few different options.

Do you recommend a rectifier AND a capacitor? Or could I get away with just a capacitor?

Also, am I under the impression that I do not need an ignition switch? I plan on wiring up a dual lead kill switch to reach to both coils to kill power.

Is my engine ground strap in an ok place? Or does that need to get re-mounted to another point?

Thank you seriously for your time and help on this! It means a lot to me getting this beauty back on the road!

Cheers!

LOUD MOUSE · Post by **LOUD MOUSE** » Wed Apr 24, 2019 8:54 pm

The BLACK LEAD is for 12 VOLTS. ..........................lm

1204_cb77 wrote:Hi, hoping to get a hand on this as I am severely struggling! I have attached pictures of what I am working with. I have no battery and no ignition key/switch. I am trying to keep this as limited as possible.

This bike has two small condensers instead of one big one mounted below the coils. You can see them on top of the coils. Each one has a single lead coming out of it. From the diagram these appear to just be grounded which I have done so to the coil mounts as you can see in the pics.

I also grounded the main engine ground to the right side condenser mount. Not sure if this is correct...

From the points plate I have green to the right coil, yellow to the left. Both to the negatives on the coils.

I see on the diagram there is a black lead from the coils that goes to the combination switch IG, which I assume is the "Ignition Ground" as of now my black lead is just hanging free as I have no switch or harness.

Being that I have no switch or power source is that keeping me from spark? I also don't have any leads from the stator wired up as you can see which I assume I don't need to simply get spark? I have set the points gap at .012 with new plugs and new MSD coil wire. Not sure how old these coils or condensers are. I tried getting a reading but didn't come out to well on that..Will try again this evening!

Thanks to all who can lend a hand on this! I really appreciate it!!!!

Max

Right Coil wiring

Left Coil wiring

Right side engine ground to condenser mount

mike in idaho · Post by **mike in idaho** » Wed Apr 24, 2019 9:05 pm

The current output from the stator wires is a/c, alternating current. A capacitor will not store a/c current, only d/c current, that's why you need a rectifier. Also the coils you have are designed for d/c current, they will work very poorly(if at all) on a/c. Some sort of regulator is also needed to keep the voltage from going too high and overheating the coils. This one here: https://www.amazon.com/Voltage-Regulato ... A3ZC4P8OAR will do the job of both rectifier and regulator for not much money.

1204_cb77 · Post by **1204_cb77** » Wed Apr 24, 2019 9:36 pm

mike in idaho wrote:The current output from the stator wires is a/c, alternating current. A capacitor will not store a/c current, only d/c current, that's why you need a rectifier. Also the coils you have are designed for d/c current, they will work very poorly(if at all) on a/c. Some sort of regulator is also needed to keep the voltage from going too high and overheating the coils. This one here: https://www.amazon.com/Voltage-Regulato ... A3ZC4P8OAR will do the job of both rectifier and regulator for not much money.

Thanks for the link.

I did find a few capacitors on eBay I will order along with this Kohler rectifier I can mount accordingly.

I am guessing then also as LM has clearly pointed out that the black lead will need 12 VOLTS. which I will connect to the capacitor.

Again and sorry to ask but do I not need an ignition switch as the capacitor will be my consistent source of 12v? Thanks

1204_cb77 · Post by **1204_cb77** » Thu Apr 25, 2019 8:02 pm

Alrighty, got that rectifier on order and have a small Yuasa battery I plan on using. Also will wire in a on/off toggle switch. I am going to go to Oreilly auto and pick up new coils and condensers too. Might as well get all the old stuff replaced so no questions asked!

Now, from the Stator there is Pink, Yellow and Brown. Pink wire I see runs to the lighting switch which I no longer have as I have a separate lighting circuit hooked up.

Yellow Runs up to the old Celenium rectifier along to the SE position on the lighting switch

Brown also runs up to the old Celenium rectifier.

I am assuming I only need yellow and brown wires running to the new rectifier?

Thanks for the help as always!

revlover · Post by **revlover** » Sat Apr 27, 2019 4:14 pm

A word about your ignition coils.... The coils in your pictures are automotive type coils. As the printing on the side indicates, an external ballast resistor is required for each of the coils. Because of their very low primary resistance, a resistor or resistive wire is used to prevent excess current flow through the coil. If you operate these coils at 12 volts or higher, excessive current flow will result and your points will likely be damaged. In addition, the combined current consumption of the two coils may be beyond the output capability of the stator. A better choice might be some universal coil designed for motorcycles. EMGO makes universal cylindrical coils which have a more suitable primary resistance and will fit nicely in the tight space under the tank. If however you insist on using the auto coils, a suitable resistor must be sourced for each coil. The resistors should be wired inline with the positive wire and be mounted somewhere with adequate air flow because of heat. Probably not the best idea if you want the wiring to remain simple though. Hope this helps.

Here is a link for the coils.
https://www.amazon.com/EMGO-Ignition-Co ... 1MNKKZ829N