Topic: 1982 cb650 nighthawk ignition troubleshooting

[BenHume]

Hi! I was having trouble keeping my bike running once it was warmed up, and so I pulled the plugs and tested them once warm and found that the plugs for cylinder 2&3 weren't firing. After letting it cool, spark returned. Both of my ignition coils appears to be originals and both tested a bit low, so I decided to order new coils/wires/caps. Sadly once the new ones were installed and tested (all sparked beautifully​) I warmed up the bike and experienced the same issue... The plugs for 2&3 cylinder weren't firing.

This leads me to believe that the issue must lie in the CDI boxes or the pulse generator. I don't know how to test either, but something is malfunctioning once the bike warms up. Any help would be appreciated.

-Ben

[evinrude7]

i don't know jack about cdi boxes but looks like if they are bad you just replace them.

https://www.youtube.com/watch?v=0ZR0FX1_icg

[DaveBarbier]

The CDI was a weak link in the 650. Not sure what the diagnosing procedure is if anything.

I may be jumping the gun but you might want to consider a different electronic ignition. I just did a write up on installing a PAMCO for a 750 on a 650. Not too difficult but requires a little machining. Check my build thread if you're interested.

[JBell]

My  1982 650 Nighthawk recently quit, and upon investigation, both coils are bad, primary side ok, firing side-no continuity.  I have ordered new coils, but wonder how both coils failed simultaneously?  Seems unlikely??  They are grounded properly and appear good, no cracks, etc.  They are over 36 years old, but the dual failure is puzzling?

[jgger]

Might help.

The SOHC/4 Technical Documentation Library

CB350 CB400F CB500 CB550 CB650 CB750A CB750F CB750KCustoms General Tech Documents

CB650 1979-1982Owners Manuals1980 CB650 (6mb pdf)1981 CB650 (6mb pdf)Service Manual (1979)CoverIndexChapter 1: General InformationChapter 2: LubricationChapter 3: Inspection and AdjustmentChapter 4: Fuel SystemChapter 5: Engine Removal and InstallationChapter 6: Cylinder Head and ValvesChapter 7: Cylinder and PistonChapter 8: ClutchChapter 9: Gearshift LinkageChapter 10: CrankcaseChapter 11: Primary Shaft and TransmissionChapter 12: CrankshaftChapter 13: Front Wheel and SuspensionChapter 14: Rear Wheel and SuspensionChapter 15: Hydraulic Front BrakeChapter 16: Battery and Charging SystemChapter 17: Ignition SystemChapter 18: Electric StarterChapter 19: SwitchesChapter 20: TroubleshootingParts CatalogCover & Introduction PagesEngine & ClutchClutch, Generator, Starter motor, CrankcaseCrankshaft, Primary Shaft, Transmission, CarburetorCarburetor, Headlight, Gauges, Handlebar SwitchesFront Stem, Forks, Wheel, BrakeFront wheel, Rear brake, Rear Wheel, Tank, SeatBattery, Rectifier, Air Cleaner, Pipes, Brake PedalBrake Pedal, Pegs, Center Stand, Rear Swing Arm, Rear Shocks, Rear FenderRear Fender, Turn Signals, Brake Light, Wiring Harness, Frame, Toolkit, IndexService BulletinsHSB 650 #1: 1980 CB650 Acceleration PerformanceWiring Diagrams80/82 CB650, 80/81 CB650C Custom

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http://www.sohc4.netadmin@sohc4.net

Go to the CB650 scroll down to chapter 17.
Sorry for the goofy way I did the link.

[JBell]

cb650sc won't start.  Coils tested bad, replaced with coils of I'net.  Seems to blue spark at plug, but still won't start.
New coil secondary tested ok for continuity/resistance, but primary side was .7 on a 200 scale on continuity/resistance, it should be 3-6 ohms, I believe.  What should I check now?
Pickup coils and spark coils appear to work and it ran fine until it quit and wouldn't start, luckily after lengthy park in my shop.  I checked coil for cyl. 1 and 4, will check coil for cyl. 2 and 3, just to be sure.  The only thing bothering me about new coils is the .7 resistance on the primary side, book says s/b 3 or 4 ohms, I think. Ideas?