Make sur the coil its self is got a ground, and dont just swap the coil wire, actually swap the coils. Start at the end of the line, plug, wire,coil, wiring,pickup coil etc..

Let us know the outcome from the swap and ground confirmation..


Also, always give more info than is needed, was any work done recently?, any accidents, any extended storage times etc.. Theres a lot of great knowledgble guys on here, but we cant help you properly with any missing info.

Incase you need it..(78,79,80)

Download Honda CX500 Custom 1978 Shop Manual | ManualsLib

www.manualslib.com

 

I recently had an issue where it was not firing on the left cylinder unless you revved it high then it would kick in. Was the coil wire itself and out of sync. Was fine for a month or so. Bike has been a bear since I got it. I've replaced the coils from my parts bike. And swapped the right and left with the same results. I will have an occasional spark on the left side every so often. Just tried swapping coils again and same result.

 

I need to know if your rear case has a cover that is vented or not vented.

the cx500 with a NON vented case, has a CDI controlled Ignition.

the one with a VENTED case has a TCI controlled ignition.

I need to know what your case is?

 

I need to know if your rear case has a cover that is vented or not vented.

the cx500 with a NON vented case, has a CDI controlled Ignition.

the one with a VENTED case has a TCI controlled ignition.

I need to know what your case is?

How would I tell what case I have?

 

In your original post, you mentioned you already swapped the cdi box, did it look like this one here?

If you have this one, then it is the actual CDI, and has a non vented case.


The ones below are the TCI ignitor boxes.

 

Looks like the first pic big box

 

Ok, good thats the better system of the two. Your bike has a low speed pickup, and a high speed pickup for ignition. each will give a ingition cdi its signal at different rpm ranges. Since you say as you increase the rpm, this tells me you have a faulty "low" speed pickup.

The low speed pick up is two seperate coils on the outside of the rotor, the high speed pickup is actually made onto the stator coil and is on the inner side of the rotor.

The stator has many smaller poles that are for the bikes electrical output, there is alo a large pole, and this large pole is the high speed pickup.

If you look on google you may be able to fine some pictures of the cx500 low speed pick up coils. Ther is a left and right low speed pickup signal. without these low speed signals the CDI can not output at low rpm, In these designs of this "dual" low speed, the left and right is seperate and one each controls the laft and righ cylinders signal to the CDI. So sounds like you have a single low speed pickup coil that is bad.

I will also add, your bike has a seperate pick up coil set for the advance as well. This unit is directly located on the back of the engine under a small plate/cover.


how it functions is this:

As the rotor spins, all three sets of pickups are giving signal, the Low speed is used at idle, as rpm increases the signal used by the cdi will swap to the high speed pickup, as the rpm continues to increase the cdi will use the pickups from the advance set, for any ignition retard/advance in timming needed. As the rpm decreases, this system will reverse.

 

Alright. The rpm problem was before I had fixed that since. It won't even run now.

 

Sounds like the low speed coils are totally bad then..

Here is the high speed on the stator, (large pole) and the two low speed coils. note this does not include a picture of the advance coils.

 

Bad news is the engine has to be removed and rear cover removed to access these. Might as well replace the starter clutch as well since you will be in there.

 

How do I test the low speed coils?

 

wow that was really designed for ease of service, wasn't it.

 

Yup sure was lol. If I swap the left coil to the right coil wire from the box ill get spark. No spark on the left side wire from the box. It won't even run so I'm not sure if its the low speed pickup. I've been battling with this bike for almost a year now.

 

there are wires coming from the pickups, to the box... swap those. when swapped, your no spark issue will switch sides. if it does switch sides doing this test, then you indeed have a puls coil bad.

 

Yes most likely. But parts are almost impossible to get. And most used stuff on eBay will leave you broken and frustrated. So with mine I made my own ignition system that works better than original and under$100.00 if interested I'll share how. Love to get my people up and running again.

 

I used car coils and two gy6 CDI units a few other touches that took some time to figure out. But running awesome.

 

Interesting idea to use stick coils.

And I like the sticker on the tank