Topic: CB550 Running at 80%

[UNFORGIVABLE]

Hi everyone!

I have an issue with my 1974 CB550. I purchased it a few months ago in good working condition. Never missed a beat and had power when I needed it. Now I have an issue with how it runs. I've been lurking on here for a little while looking for help and insight and now it's time to ask for help. Thanks in advance.

Summary:
Out of the blue on one ride home from work, I suddenly felt a vibration at all RPMs and I've been trying to track this issue down for a few months now. The bike starts up fine and runs "okay". It also less power and some hesitation. All cylinders are firing since all 4 the pipes get hot. I checked for spark on all cylinder and all have a purple spark when rested on the engine. It feels like it's running of 3.5 cylinders if that makes sense. Almost like its running at 80%. It definitely lost the engine sound that I remember.

Brief History
During the time when this started I had recently installed an electronic ignition to replace the points plate since one of the condensers went bad for Cyl 2 and 3. After installing the electronic ignition the bike was restored to full running capability. Then this issue starts one month after installing the electronic ignition. Since the arising of this issue, I've replaced sparkplugs, installed a new electronic ignition, took that out and replaced the condenser in the points system, cleaned the carbs twice, checked/ adjusted valve clearance 3 times, Set dynamic timing with timing light, set static timing with points plate, new rubber carb boots, installed new ignition coils, adjusted cam chain tensioner twice, carb sync at the end of all of this, and replaced the battery (Original battery died a week or two after the start of the issue to the point where it would hold a charge for any length of riding. Never put it on a plug-in charger). After all of this, No change in performance!

I recently bought a multi meter and tested the voltage at the battery (the new 1 month old battery) as of last night (approx 11.87V- bike off) and the voltage at the Black/White wire going to the Coils (Approx 10.7V bike off). The power to the Black/White wire to coils never sees above 12V even when running the bike. the battery hovers around low 12V when running. I don't know what the Voltage was when it was new and charged.

I tested the 3 yellow stator wires for continuity and resistance. No continuity to ground and .3 Ohms between each wire.

I rode the bike last night with no gas tank at night and I saw no spark or arcing anywhere in the coil area.

I plan on looking at the Rectifier/ Regulator unit next and a new battery.

Questions:
Do I have a short somewhere?
Are my coils getting enough power?
Charging issues?
Rectifier/ regulator problems?
Are some cylinders not getting enough fuel?
Bad Compression?
Skipped Timing?

Please Help Guys!! Thank You.
 

[Scott S]

 What ignition? If it's the Dyna S then that low voltage will make it do crappy things.

[UNFORGIVABLE]

The voltage you are seeing is a major cause of ignition problems. Best you begin tracing the source of voltage loss, or charging issues.

Key OFF, battery should read 12.8v or better. Running at 3,000 RPMs you should see ~13.8v but never more than 14v lest you cook a battery (you might see spikes above 14v depending upon meter and other momentary events).

If the BLK/WHT wire is well below 12v with the engine running, the coils will not fully power the plugs, resulting in poor combustion/power.

Thanks for the replies! Yes I'm very concerned about the low voltage. I'm trying to track it down, looking for shorts/bad wiring. Gonna test the regulator/rectifier soon.

What ignition? If it's the Dyna S then that low voltage will make it do crappy things.

Yes I have the Dyna S Ignition. But I just recently replaced the bad condenser on point points ignition and reinstalled that last night. I have most of my power back, but the issue still resides. I'm just exhausted with this process.

[flatlander]

a good starting point would be to go over all electrical connections. check that the wires are intact, and clean and polish all connectors. also include grounds and fuses. really the whole lot. after all those years they may be corrosion or defects or someone tinkered with it...
take the time to do that and once done, measure again. if you then still have too low voltage it's time to check individual components.

[UNFORGIVABLE]

a good starting point would be to go over all electrical connections. check that the wires are intact, and clean and polish all connectors. also include grounds and fuses. really the whole lot. after all those years they may be corrosion or defects or someone tinkered with it...
take the time to do that and once done, measure again. if you then still have too low voltage it's time to check individual components.

Thank you. That's a smart approach.

[dave500]

you haven't mentioned the spark plug caps,they may be old and have high resistance?