Motorcycle Repair: 1974 CB550 electrical issue??, flasher system, petcock

Question
Hi BILL,  I was driving my motorcycle around town, then decided to get on the highway.  At about 60mph I turn my signal on and it started flashing twice as fast as normal.  Then about 1 mile later it started to run eratically.  I took the next exit and the bike died at the bottom of the ramp.  I tried to start it but it wouldnt start.  I finally got it to run after a few tries but only when it was fully choked.  I after a few minuets and a dozen trys later it stayed running and ran fine with the choke off.  I drove it a few miles home and everything was fine. tried it again today and worked fine.  any ideas?  btw it did install a Dyna electronic ignition in it.

Answer
Ben, I'll start with the simple things... did you run out of gas in ON position of the petcock? Did you open the gas cap? If the cap vent is plugged up, it can slow/stop the fuel flow to the carbs. Did you recently buy fuel? Was the petcock in On or Reserve at the time?

When turn signals flash ultra fast, generally one bulb is bad in that side's flashing circuit. Now, if your battery was low and you are used to some slow flashing, once you get out to the highway, the charging system is kicking out full voltage which will also speed up the flasher system. If the voltage regulator is malfunctioning, then the bike could get into an over-voltage condition which again will cause the lights to brighten up and flashers to speed up.

Start with the basics: Is the battery a lead-acid type? If so, is it full of water/acid? If so, is the battery fully charged? Is the battery able to pass an electrical load test? If so, then what is the voltage output to the battery when you rev the engine to 3k rpm?

If the charging system is over-boosting the output, it could endanger the the electronic ignition or cause it to shut down, depending on the circuitry inside.

When bikes stall out, usually the cause is fuel or electrical. Checking for fuel in the tank and making sure that the petcock is in Reserve after a stall helps to eliminate the fuel concerns.

If the lights go dim, the horn barely works, turn signals quit flashing then you have electrical issues. The charging system has a separate voltage regulator, rectifier, field coil, stator and wiring associated with this function. Any one of these items can fail after 37 years. It is a good idea to check all electrical connections as well as the ground paths on the bike.

Bill Silver