Author Topic: 1979 CB650 (Read 1564 times)

scott jones · « **on:** September 29, 2021, 02:57:07 PM »

HI there. Scott here. I bought this bike as a basket case. It didn't have a starter solenoid on it. I hooked my jumper pack up the the cables that were there & realized I had the cables hooked up backwards. Now I have no spark. I installed new coils & new spark units. Still no spark. What damage to the ignition system do you think I did?I haven't replaced the voltage regulator/rectifier yet. I have read online that it can be burned out quickly.

Alan F. · « **Reply #1 on:** September 29, 2021, 05:03:26 PM »

Exactly which cables did you connect your jumper pack to? There should be a section in the factory manual on testing the electrical system components individually with an ohm meter to determine which is out of spec or failed, and which are good. You'll need to go through these tests with your bike. Opinions may vary, good troubleshooting with a factory service manual will uncover the real truth.

TwoTired · « **Reply #2 on:** September 29, 2021, 06:44:08 PM »

If you hooked up battery voltage backwards to the bike, expect the rectifier to have burned up, as well as the wires to it. Any of those wires routed through the wire harness also burned up wires running parallel to them. Get a wire diagram and look at the wires routing from battery to rectifier. Chase them physically, and replace all burnt wires you find.

Everything else should be ok if you didn't have the key switch on, as that would have prevented reverse polarity from reaching those devices. If you had the key switch on, anything with transistors in it likely fried when driven with reverse polarity.

You might want to review basic electricity relating to polarity of devices. Some lessons are more expensive than others.

Cheers,

scott jones · « **Reply #3 on:** September 30, 2021, 04:25:27 AM »

As I said there was no starter selonoid on the bike. I hooked the jumper pack to the starter cable & the battery ground cable. These were the only 2 cables I saw. The main wiring harness to the starter selonoid was not hooked up because there was no selonoid. Now that I have everything hooked up properly I still have no spark.

goodtryer · « **Reply #4 on:** September 30, 2021, 04:57:31 AM »

Simplified diagram of the ignition circuit on page 4 in this PDF: http://manuals.sohc4.net/cb650/service_manual/SM65079_17.pdf
Page 5 in the PDF shows how to troubleshoot the spark unit.

Page 4 in this PDF has the diagrams of the handlebar switches: http://manuals.sohc4.net/cb650/service_manual/SM65079_19.pdf

Good luck!

scott jones · « **Reply #5 on:** September 30, 2021, 06:49:15 AM »

Thanks goodtryer. I have access to those wiring diagrams. I have looked at them a hundred times. I'm not good with electrical. Might get rid of the bike & cut my losses. It's a shame because the bike is excellent cosmetically & has low miles.

goodtryer · « **Reply #6 on:** September 30, 2021, 07:53:42 AM »

I know the feeling. I dread dealing with electrical gremlins, too. But don't give up. Just break the problem down into smaller pieces.

If I had to guess, I'd say your problem is in the handlebar switches. Can you trace the 12V (or just continuity, if you want to work without the battery) from the connection going into the handlebar and to the connection coming out. In the headlight bucket, find the black and black/white wires that come from the right handlebar wires. Disconnect them and touch the leads from your meter, one lead to each wire. With the stop switch in the RUN position, do you get continuity? And no continuity when you move the switch to STOP?

One other question: you said "no spark". Is this on all plugs or only one?

scott jones · « **Reply #7 on:** September 30, 2021, 08:10:09 AM »

Ok thanks goodtryer. I'll do that & let you know what I get.

scott jones · « **Reply #8 on:** October 01, 2021, 04:05:21 AM »

Good morning. I tested the run/stop switch. I have continuity when the switch is in the run position & no continuity when the switch is in the stop position. So that appears to be working correctly. What's the next step please? Thanks, Scott.

goodtryer · « **Reply #9 on:** October 01, 2021, 04:51:28 AM »

Next, test the voltage at the Spark Unit. Do this with the key on and the stop switch set to RUN.

The procedure is pictured on page 5 of this PDF: http://manuals.sohc4.net/cb650/service_manual/SM65079_17.pdf

You didn't answer the question about the spark plugs. Did you test more than one plug?

scott jones · « **Reply #10 on:** October 01, 2021, 06:04:50 AM »

I have no firing on any plug. Scott

scott jones · « **Reply #11 on:** October 01, 2021, 06:05:41 AM »

Ok I will test the spark units tonight. Thanks!

scott jones · « **Reply #12 on:** October 01, 2021, 07:30:26 AM »

Mr Good tryer. I should also mention that I'm having trouble with my neutral switch. When the bike is in neutral the green light does not come on but I can ground the switch & the light comes on. Don't know if this has anything has to do with my no spark situation. I have cleaned the switch & the rotor. I know the rotor is touching the switch properly when the bike is in neutral. I also have the clutch switch on the LH handlebar bypassed. Thanks for all of your help. Scott.

goodtryer · « **Reply #13 on:** October 01, 2021, 07:55:03 AM »

Ummm, yeah, the neutral switch and the clutch lever switch could have an impact...

When you ground the neutral switch and the light comes on, do you get spark at the plugs?

scott jones · « **Reply #14 on:** October 01, 2021, 08:39:40 AM »

Thats a good question sir. I don't know . I haven't tried that yet. I thought of that too. I will see tonight. Are you available this weekend for more instructions? Scott.

goodtryer · « **Reply #15 on:** October 01, 2021, 10:05:39 AM »

Yes, I'll be around. Send a PM with your cell # and we can talk.

scott jones · « **Reply #16 on:** October 01, 2021, 11:23:04 AM »

I PM'd you my cell. I have to work tomorrow. I'll probably work on the bike most of the day Sunday. Maybe tonight a little if I have time. Scott.

goodtryer · « **Reply #17 on:** October 01, 2021, 11:47:35 AM »

Got it. I'll contact you shortly.

scottly · « **Reply #18 on:** October 01, 2021, 07:50:43 PM »

Quote from: goodtryer on October 01, 2021, 07:55:03 AM

Ummm, yeah, the neutral switch and the clutch lever switch could have an impact...

No, the neutral switch and clutch lever switch only affect the operation of the electric starter, and have nothing to do with spark at the plugs. Do you have 12V at the black/white wire coming from the kill switch, with the switch set to run and the key switch on?

scott jones · « **Reply #19 on:** October 02, 2021, 10:39:57 AM »

Don't know Mr Scottly. I was told to check the start/run switch for continuity. I did not check to see if I had 12 volts on the black/white wire. I will check that tonight. Thanks. If I don't have 12 volts on the black/white wire where might else I check for the problem? Thanks.

scott jones · « **Reply #20 on:** October 02, 2021, 10:46:44 AM »

I do see from the wiring diagram the black/white wire feeds 12 volts to the ignition coils & the spark units. I do not have power to the coils. I checked that the other night with a test light. Don't know about the spark units yet but with no power to the coils I assume I have no power to the spark units since they are on the same circuit. Correct?

TwoTired · « **Reply #21 on:** October 02, 2021, 10:56:40 AM »

Quote from: scottly on October 01, 2021, 07:50:43 PM

Quote from: goodtryer on October 01, 2021, 07:55:03 AM
Ummm, yeah, the neutral switch and the clutch lever switch could have an impact...

No, the neutral switch and clutch lever switch only affect the operation of the electric starter, and have nothing to do with spark at the plugs. Do you have 12V at the black/white wire coming from the kill switch, with the switch set to run and the key switch on?

Er, the 650 has no kick start, right? Not going to get spark without the engine turning over. Or, are we driving the engine turnover by spinning the rear wheel? I never checked for spark that way. :-)

Cheers,

scott jones · « **Reply #22 on:** October 02, 2021, 11:03:42 AM »

No sir. My starter works fine from the starter button. All the lights work properly too.

TwoTired · « **Reply #23 on:** October 02, 2021, 02:35:09 PM »

Quote from: scott jones on October 02, 2021, 11:03:42 AM

No sir. My starter works fine from the starter button. All the lights work properly too.

Then your neutral switch and/or clutch switch are working. Subtle, that.

Cheers,

scottly · « **Reply #24 on:** October 02, 2021, 07:20:10 PM »

Quote from: scott jones on October 02, 2021, 10:46:44 AM

I do see from the wiring diagram the black/white wire feeds 12 volts to the ignition coils & the spark units. I do not have power to the coils.

Check the black/white were it comes from the kill switch. If no power, check the solid black wire that feeds the kill switch. If no power, start tracing the black wire back towards the ignition key switch. The black wire also feeds 12v to other things, like the brake light switch and voltage regulator. If you have power in those places, the problem *might* be in the headlight bucket.

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Author Topic: 1979 CB650 (Read 1564 times)