Topic: 1975 CB550 Issues. Is this normal?

[shepard]

I have been quite successful in restoring my 1975 CB550 K1 and it nows runs relatively reliably. 

However, two recent events have warranted my attention:

1. Today my bike stalled at a light today when I tried to engage into 1st as the light changed.  I switched my petcock to reserve in case that was the problem, quickly got the bike going again.  It seemed that the bike was not in the mood for low rpm's so I goosed the throttle to my nearby parking area for class.  When I got to my parking area the bike died after idling for about 3 seconds.  I had checked my gas before I left the house and I appeared to have about 1/4 to 1/3 tank, but I switched to reserve when it stalled because my gas tank has deceived me in the past.  Regardless, after class I coerced the bike into starting by turning off the headlight.  I goosed the throttle to the nearest gas station, filled up the gas and the bike ran well for the rest of the day.  It always seems that the bike runs much smoother when I have a full tank of gas.  Is this normal?  I assume that this could be a symptom of an dirty petcock filter or a clogged reserve nozzle but both nozzles flowed ok last time I checked.

2. A couple weeks ago I awoke one morning to discover a dead battery, but I assumed this was caused by a 1 mile, low RPM ride the night before.  I know that these bikes have somewhat poor charging systems and I thought that may have been the culprit, but I am also suspect of the charging system parts on such an old bike. Also, a couple months ago I was riding and the bike died and I had to take my battery home to charge and bring it back to the bike and then it started fine.  Hence, my suspicions of the charging system.


Diagnosis: At this point I am thinking that my woes are a result of either a poor spark and poor gas flow, or more likely some combination of the two.  Does that sound appropriate? 


Additional info:  My spark has always seemed weak to me, but I'm no expert and the bike runs well with a full tank.  Additionally, my headlight seems relatively dim, although I believe this may be normal for these old bikes.  I am also suspect of the points since they are probably original.


Also, does anyone have any further ideas?  Should I switch to CDI, check the stator, or possibly install a more appropriate headlight bulb?

[mattcb350f]

On these bikes, at least the 350F anyway they have a rather long tube sticking up out of the petcock on the gas tank. This is where the fuel flows into in the "on" position. When you think you have enough gas, like 1/4 tank, that is barely enough to fill the tank enough to go down this tube. what I'm saying is that there's a good chance that what you thing is 1/4 to 1/3 of a tank probably isn't enough to flow down the "on" tube.

Now the other problem, get a multimeter and check to see if the bike is charging...

 Matt.

[OldSchool_IsCool]

Turn off your petcock and pull the fuel line off the carbs.  Measure the amount of time it takes to fill and 8 ounce cup.  If it's 15 seconds or less, you are good with fuel flow.  Test the reserve position too.

If you have an in-line fuel filter, either ditch it or make sure it is mounted vertically.  A horizontal mounting can trap air and restrict fuel flow.

Drain your float bowls one at a time into a clear jar.  Any water or crap in there?

Sure sounds like you are having charging trouble.  Spend a day with sand paper and micro files to clean up all electrical connectors throughout the bike.  Pack them with dielectric grease to slow corrosion.  Check the acid level in the battery.

Measure the voltage across your battery.  With the engine off, you should see 10-11 volts minimum.  11 to 12 volts with the engine idling below 2000.  Voltage should peak at 14 volts when reved to 3500 and above.  If the voltage is lower then this, you have charging/wiring issues.  If voltage exceeds 14 volts, you are cooking your battery