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Author Topic: CB360 spark problems  (Read 255 times)

Offline tahitianrider

  • Posts: 23
    • tomracingdesigns.com
CB360 spark problems
« on: Jul 13, 2018, 17:21:55 »
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 :)
'94 BMW K75 Racer
'84 Yamaha XJ 600 "Rocket" Racer
'76 CB 360 old school cafe
'96 CM 125 Brat bike
'80 CX 500 soon to be racer
'K15 MT-07 "The only bike I can actually use everyday" lol
www.tomracingdesigns.com

Offline advCo

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Re: CB360 spark problems
« Reply #1 on: Jul 13, 2018, 18:15:27 »
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.
"He broke the mirrors off his Cadillac, 'cause he doesn't like it looking like he looks back."

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Online irk miller

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Re: CB360 spark problems
« Reply #2 on: Jul 13, 2018, 19:16:05 »
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.

Offline raptormeat

  • Posts: 398
Re: CB360 spark problems
« Reply #3 on: Jul 13, 2018, 23:13:04 »
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.
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Online irk miller

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Re: CB360 spark problems
« Reply #4 on: Jul 14, 2018, 01:23:06 »
I paint the inside of my points cover with liquid tape.  That takes care of the potential for ground on the cover.

Offline tahitianrider

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Re: CB360 spark problems
« Reply #5 on: Jul 14, 2018, 06:15:25 »
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 ?
'94 BMW K75 Racer
'84 Yamaha XJ 600 "Rocket" Racer
'76 CB 360 old school cafe
'96 CM 125 Brat bike
'80 CX 500 soon to be racer
'K15 MT-07 "The only bike I can actually use everyday" lol
www.tomracingdesigns.com

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Re: CB360 spark problems
« Reply #6 on: Jul 14, 2018, 09:09:27 »
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.

Offline Sderbyshire

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Re: CB360 spark problems
« Reply #7 on: Jul 14, 2018, 10:05:18 »
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



Offline tahitianrider

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Re: CB360 spark problems
« Reply #8 on: Jul 14, 2018, 10:17:19 »
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.
'94 BMW K75 Racer
'84 Yamaha XJ 600 "Rocket" Racer
'76 CB 360 old school cafe
'96 CM 125 Brat bike
'80 CX 500 soon to be racer
'K15 MT-07 "The only bike I can actually use everyday" lol
www.tomracingdesigns.com

Online irk miller

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Re: CB360 spark problems
« Reply #9 on: Jul 14, 2018, 10:49:46 »
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.