CB350Four Not Charging when hot.

[fastlee84]

Hi Guys,

I have a 74' CB350Four. I have completed overhauling my pistons and redid my Carbs. All are running smoothly.
Until I realized my headlights aren't as bright as it's used to.

After riding for a few days, my bike died when I stopped at the stop light. and it wouldn't start.

I checked the battery and its completely died. I charged the battery with a charger and fixed it back to my bike and its able to start again.

When I checked the rectifier its working well and the stator coil are giving the right voltage and charging the battery at average 13V.

Then I realized something, when my bike gets hot, its not charging the battery.

Have anyone encountered this before? My bike gets hot quite fast.

Appreciate any comments on how to solve my problem.

Btw the rectifier was changed to an aftermarket a year ago.

Regards,
Fazdli

 

[carnivorous chicken]

Then I realized something, when my bike gets hot, its not charging the battery.

Have anyone encountered this before? My bike gets hot quite fast.

How did you determine this?
Sounds like it might just be a dead/old battery, but I'm curious to hear others' opinions.

 

[fastlee84]

Hi,

Basically, its charging fine initially but when I start to run the engine and it gets hotter, the voltage drop to 12V. instead of the 13V.

When I let the bike cool again, I start it up, increase the RPM, it charge at 13V again..

That's what confuses me.. I know when metal is heated up, it expands, does this apply to the stator area? makes it harder to turn? I don't know. Help..

I'll try to re-coil the stator first and see how it goes.. Is that a good step to do?

regards,
Fazdli

 

[BCBarker]

I think you are correct. Sounds like there maybe a break in the coil field that when the motor heats up the crack/coil becomes larger. If you can find the crack, you can try to repair. Otherwise you need to either rewind the coil, or find a replacement. I have a replacment if you want to go that route.

 

[mydlyfkryzis]

Rectifiers can fail hot, so can regulators. As they run, the get hot. Not unusual.

When it is hot, get a voltmeter. Disconnect AC lines from alternator. Measure AC volts ...if good,

The regulator can be disconnected. You would then have unregulated DC volts, but it won't be a problem for testing purposes. If you disconnect regulator and volts come up, then you know it is the Regulator.

If not, then replace rectifier. These are cheaper, easier options then replacing the stator. If the rectifier does not help, then you know it is the stator.

Eliminate one thing at a time.

 

[fastlee84]

Rectifiers can fail hot, so can regulators. As they run, the get hot. Not unusual.

When it is hot, get a voltmeter. Disconnect AC lines from alternator. Measure AC volts ...if good,

The regulator can be disconnected. You would then have unregulated DC volts, but it won't be a problem for testing purposes. If you disconnect regulator and volts come up, then you know it is the Regulator.

If not, then replace rectifier. These are cheaper, easier options then replacing the stator. If the rectifier does not help, then you know it is the stator.

Eliminate one thing at a time.

Ahhh... I will do it tomorrow morning.

A newbie question (I know you would slam your helmet to my head kinda question): When I do all this, my bike would have been running quite a while and I have to remove/disconnect the wires while its still running right? I guess it should be done while its running.

Step 1: Measure the AC voltage after disconnecting AC Lines from the rectifier/regulator.
Step 2: Connect back the AC Lines and measure from the regulator. (Disconnect the regulator and measure from the rectifier?)
Step 3: Measure the rectifier output when the regulator is removed? To see whether the voltage keep rising, right?

Is this right?

 

[mydlyfkryzis]

Rectifier has 4 lines to it ...2 are AC, 2 are DC.....Won't hurt to measure both at the rectifier.

You have a permanent magnet alternator? correct? If so, regulator shorts to ground to keep voltage down. Disconnecting the three lines to it will not hurt for testing. One is ground (green), one is Batt 12V (black) the other should be the AC line that gets grounded. With all three disconnected, you will have unregulated DC..At lower then 4-5K rpm, you won't even put out enough to rise above 14 volts.

So you would check the batt volts, while holding the engine about 5 k rpm.

If the voltage is rising, wait till it bets to 15V to stop the test. If it is low, battery volts 12.7 or less, then you are not charging.

 

[fastlee84]

Thank you MydLyfkryzis for being patient enough to explain in detail. Really appreciate it! And I really understand it now.. I'm gonna try it out soon!

Thanks!