CB360 spark problems

tahitianrider

Been Around the Block
Hi!
I have picked up a while ago a CB 360 that was running but with many problems: sometimes running on 1 cylinder at idle, severy misfiring when riding, stalling when hot and couldn't restart etc.

I suspected of both fuel and ignition problems, so I did a lot of work on it :
- Ultrasonic cleaned the carbs and rebuilt them with new parts (jets, o-rings, mixture screws, etc.)
- Tank was rusted with a mix of rust and epoxy (bad previous epoxy job) so I'm cleaning it right now, but testing the bike on my workshop fuel bottle anyway.

On the electrical system :
- I suspected a bad ignition timing, and when checking it with a test lamp it was indeed bad. So I installed new contact breakers and set the ignition timing correctly (it is hard to get it perfect but I'm very close : it fires at less than 1mm from the fire timing marks)

I tried to start the bike (from a workshop fuel bottle so the carb do get fuel correctly) but it wouldn't start at all (although I was starting before I tried to fix everything)
When check the sparks (with a brand new plug of course) I have no spark at all on the right cyl, and a weak blue spark on the left cyl.
The ignition coils are really warm so they get power. But they look like the original ones, they look very old and not in a perfect shape lol.

I would like to know if I can check other things before trying to order new parts (coils, condensator...) ? or do do the problem comes from the coils ? should I try to replace them first ?

Thanks a lot for the help and sorry if a similar problem has been posted already, I did search the forum, I already learned a lot on ignition timing that way :)
 
Coils could be suspect. First make sure you have power TO the coils with a test light. From there, you can test the primary and secondary resistances on the coils to determine whether they are within spec or not using a multimeter.
 
Primary should be 3 ohms and secondary around 14 ohms. If you have resistor caps and testing shows infinity on secondary resistance, take the plug caps off and test without to rule out the caps. You can test the caps off the wire.
 
I never knew this one until yesterday, but it explains weak spark, Check the resistance between the condenser bracket (gold) and ground, the condenser may have a weak ground. I'll be honest the best thing to do is buy a refab wiring harness, new coils, and an e ignition, about 400 total. Also make sure the points wire is not grounding on cover, take cover off and test.
 
I paint the inside of my points cover with liquid tape. That takes care of the potential for ground on the cover.
 
Thanks for you replies!! :)

So I tried tout measure my coils but I'm not really sure how to do it? I tried to put the multimeter on both each side of the coils where thé cables connect. I get nothing on the right coil and "0.00" on the left coil. But the right cool has some kind of hard plastic goo on its terminals, looks like a 20 y/o fix.
I think I'll be better off ordering new coils right away, wouldn't I ?
 

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To test primary, you put each lead from the meter on each terminal for the coil. You can plug them into the ends of the coil leads. To test the secondary, you take one meter lead and plug it into the spark plug cap and leave the other meter lead plugged into a coil wire. A good coil is a good coil. I've actually repaired those old coils to run them by pulling the spark plug wire out, trimming the end to get a clean wire, then plugging and epoxying it back in.
 
The coils on my cb360 look that bad and work fine!

A methodical testing approach is needed, the system is simple.

Primary circuit get power from ignition and earth when points are closed
Secondary earths via the spark plugs as the induced voltage when the points open os ‘large’

So if you have a working primary circuit, ie power and points, then as long as the coils are functional, check their resistance, it ‘has to work’ :)

Steve
 
So I checked the coils corectly this Time, this is what I get :
Right coil : primary 00 ohms, secondary 17 ohms
Left coil : primary 00 ohms, secondary 19 ohms.

Not sure what this means ? Especialyy the "000" Reading ?
I tested primary but connecting the meter leads tout each wire coming out of the coil and secondary from plug boot to ground wire out of the coil.
 
You have a break in your primary. It could be that the wires need re-soldered or they're really corroded. Just to be sure, you could make sure the leads are good and clean. Since you got a good reading on the secondary with ground, you can test with the other wire to see if you still get nothing. Also, test your meter by touching the two leads together. Usually, you get about .5 ohms or so, but just make sure it's not a crazy number like 3 ohms.

I've had to repair stock coils by replacing leads on the primary side. Sometimes, they get bent back and forth, and pulled enough that they get disconnected where the leads go into the coil body. You have to remove the old epoxy, clean the contact point, and solder a lead back on.
 
I tested the secondary again with the other wire that goes to the contact breakers. I get a solid 19.5 on the left and 17.2 on the right , so about the same.
When connecting my 2 meter leads together I get 000.

The leads on the coils are far from clean Indeed but since I have the same secondary Reading with the other wire doesn't that mean that it may not be thé problem ?
 
What setting do you have the meter when testing primary? It should be on 200.
 
So I found a great deal on some coils and installed brand new coils along with new plug wires and cap.

Yet the bike didn't fire up. So I check the right cyl plug: no spark at all, then I wanted to check the left cyl and suddenly no more power at all: the main fuse blew up...
So I'm pretty sure there is a short somewhere... The wires at the points cover seems fine.

The I checked the wiring harness, which was a total mess... The previous owner made this bike a cafe racer and did a terrible job pretty much everywhere. 75% of my work on this bike is about fixing the mistakes he made...

So in the harness, first there are a ton of unplugged female terminals, well I guess that is because he removed all the speedometer and techometer units...
They were somehow insulated though.
BUT I found an unplugged white/red (or green/ red? Im color blind...)wire that was not insulated at all and touching the frame. Givien its color I'm pretty sure it has power and may have cause the short.
I now need to find what this wire is and where to plug it.

Oh and many terminals were loose too which may explain why I had no spark ? But the coils did feel hot when I tried to start previously...
 
So on the wiring diagram there are :
- One green and red wire: this one goes to the starter magnetic switch and the clutch switch.
- One light green and red wire: this one is for the neutral indicator light.

I'm thinking this is the light green and red wire for the neutral light isn't it? Since the previous guys removed all the indicator light and did a terrible job, I would not be surprised if he just let that wire like that after removing the neutral light without even insulating it...
So it may have cause the short and blew up the fuse, but may not be the cause for no spark at all.

Maybe my kill switch is faulty?
Unfortunately I have to wait to receive my new fuses to figure this out
 
that might be your problem. again, check that condensor mount to ground resistance...the one with all the dust on it...

also, this is worth it, no more fuses.
https://revivalcycles.com/products/waterproof-3-circuit-breaker-block
 
Yes I'll check that, I also have a brand new condensor I didn't installed yet, I will install the new one and check that ground. What should be the resistance from mount to ground?

That circuit breaker looks nice indeed
 
So I installed the new condenser and insulated the wires terminal that were not with electrical tape.

I didn't had 15A main fuse so I used a 10A fuse from a CX500 Sport I had laying around,

I turned the ignition key on, it had power for about 30sec, didn't had the time to test for spark before the main fuse blew up again...

I find this weird... it didn't blew main fuses up before... then I changed the coils and it starts blewing up fuses... I mean, if there is a short somewhere on the wiring harness, why did it not happened before?

Oh and do you guys know if the CB uses fast fusion 15A fuses or slow fusion 15A fuses?

Thanks again for all the help
 
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