Topic: 81 cb650 no spark or start

[Bjones89]

Hello everybody I have a 81 cb650 that won't start it has no spark, I thought it was the coils I tested the coils and got a reading of 2.6 for BOTH coils is this too low?

[Airborne 82nd]

check to see if you have 12v at the coils should be a black and white wire.Do you have the kill switch off

[Bjones89]

I tested the coils at the prongs with the wires off with no battery and switch off

[Airborne 82nd]

I tested the coils at the prongs with the wires off with no battery and switch off

I understand how you tested the coils but when you said you have no spark then you need to know if the coils are being told to spark and to do that you need to see if there is voltage ( about 12.6vdc) on the the wire that you took off of the coils 

[Bodi]

I believe the 1981 CB650 has an electronic ignition: where the points would have been there's a pulse generator. So diagnostics for a points system are not relevant. Coil resistance... I do not now what is correct for this system. Often electronic ignitions use coils with lower resistance than what we are used to with points.
The ignition unit can fail. It is not user serviceable. Connecting a battery backwards will kill them instantly along with the rectifier.
But make sure all the wiring is connected as per the factory wiring manual, that your fuses are OK, and cleaning the harness connectors is useful.

[DaveBarbier]

That resistance value for the coils is good. They’re about 2.5 ohm coils. You’re getting no spark on any spark plugs when you hold a spark plug against the engine case while cranking the engine over? Battery voltage good and engine and battery grounds are clean and secure?

How do the spark units look? Burned or melted? Those are notorious for crapping out in the 650. Follow the blue and yellow wires from the ignition pulse generator to find the spark units.

Is this a new issue or has the bike always done this?

[Bjones89]

Just got the bike... I don't know if the CSI boxes work... I am getting 12.50 volts out of battery..ive had the spark plugs against the head and battery leads are clean

[Bjones89]

How do I go about testing reg/rect I know the Cdi boxes can't be tested ...when I test the bullet ends that comes off coils and goes to the Cdi do I put my multimeter red probe into the bullet connected and black one to a ground?  Do I have battery connected?

[DaveBarbier]

The 650 doesn’t use a CDI ignition. It’s a transistorized ignition. But that doesn’t matter much aside from terminology. Just don’t go searching how to troubleshoot a CDI ignition because it won’t translate to your bike.

Do you have 12v going to the ignition plate?

Do you have 12v going to the coils?

I’m not sure if this will work on the 650 (I have a 650 but a different ignition), but you can try to connect a test light to the yellow or blue wire going INTO the spark units and then to ground. Turn the key to ON with kill switch to RUN and slowly turn the big nut on the ignition clockwise and when it gets to the F for 1/4 or 2/3 (depending on which wire [yellow or blue] you have the light connected to) the light should turn on. I believe blue is 1/4 but I forget exactly. That will determine if the ignition module is putting out a signal to the spark units. You can do the same test for the blue or yellow wires going into the coils.

This test will work with points and also the Dyna S which I have. Unsure if the stock ignition works with this test but it’s worth a shot.

[Bjones89]

I have a new battery in it it says it has 180 cranking amps is that enough?

[DaveBarbier]

I have a new battery in it it says it has 180 cranking amps is that enough?

Maybe others can give their insights but my battery is 210. I’d bet you’re ok if you’re not cranking all the time. 

[Bjones89]

Sorry the battery I have coming is 12v with 12 amps per hour and 140 cold cranking amps is that enough? The brand new battery I have is 12v 4 ah and 40 cca I think that's my problem lol... I hope

[DaveBarbier]

You should still be able to get spark though. CCA is just the potential energy the battery can supply for starting.

I’d look into the other stuff that was suggested.

[Bjones89]

OK next up on checklist is ignition... Do anybody know the resistance readings on a 81 cb650 ignition pulse generators? Then if it ain't that it's gotta be the Cdi boxes I feel I'm getting closer for some reason... I AINT GIVING UP!

[Bjones89]

Oh here's my bike she's beautiful I wish I can get her running it's gonna be green to copper color changing and brown grips and seat I named her repzilla cuz of reptar from rugrats and godzilla cuz...well they are green and I like them lol

[scunny]

heres a link
http://www.honda4fun.com/pdf_man_officina/pdf_manuali/CB650/CB650_Manual_10.pdf

[DaveBarbier]

Won’t really make a difference, but your ground wire is in the wrong place. Should be attached to the engine bolt that the rear brake switch attaches to. If I were to get this bike I would see that misplaced ground as a warning to go over the entire electrical system.

You still haven’t answered if you have 12 volts to the coils or ignition plate.

[Bjones89]

It ran like that with the ground there... How do I check for 12 volts to the coils and ignition plate

[Bjones89]

Also I did the tests the bike manual told me to do and everything checked out coils and ignition resistance so the manual says replace the spark units(ignitors)

[DaveBarbier]

Also I did the tests the bike manual told me to do and everything checked out coils and ignition resistance so the manual says replace the spark units(ignitors)

Those are the weak points in these ignition I hear. I see used ones that say they’re in good shape on eBay.

For checking power, there is a black/white wire going into each coil. Take your multimeter on DC volts and use the red probe to probe the connector where that wire goes into the coil and put the black probe on a ground or battery negative terminal. With the key ON and kill switch set to RUN you should get about battery voltage. Like 12 volts. It will be a little less, like if the battery reads 12.8 volts the coils might read 12.6 volts. That’s normal. Test each coil.

Same test for the spark units. Find the black/white wire that goes into the plug connector for them and test each one.

As for the green/yellow ground wire on your engine, it will most likely work that way but it’s not as designed by Honda. Also it looks a bit ugly. The stock place makes it more hidden. Also that wire looks a little thin. What gauge is it? Looks about 8awg? Should be at least 6awg. Lower the number, thicker the wire. 

Wiring diagram: http://manuals.sohc4.net/cb650/technical_reference/WD650.jpg

[Bjones89]

I didn't think u could test a spark unit... And I agree on the ground it is ugly where do the stock wire go

[DaveBarbier]

I didn't think u could test a spark unit... And I agree on the ground it is ugly where do the stock wire go

You’re not testing the spark unit that way. Just seeing if it’s getting power. If you aren’t getting power to either the coils or spark unit, then your problem is before those things.

Stock ground cable goes here:

[Bjones89]

 Ohhhhh OK... And that ground wire is going there soon

[Bjones89]

OK I tested the coils to see if I'm getting g 12 Volts one coil says 11.83 the other 11.93 is that good?

[DaveBarbier]

That with engine off, right? Should be over 12 with the engine on and idling. As far as I can remember I get about 13.8 volts at the coils when idling...something like that.

I would say that it’s likely the spark units are bad. If they’re not too much I’d get some used ones and pop them in.