Topic: 1978 CB550 electrical issues

[mkmob]

Hi all,

I've been having some electrical issues with my bike and I'm kind of stumped. So, I was hoping someone out there might have an idea about what's going on. This is my first bike, so I'm still very new to all this. Here's what going on:

I've been working on this bike over the winter and have done a few things; new spark plugs, new points and condensers, and adjusted ignition timing. I was worried that there might be an electrical issue because when I bought it the battery was shot. It was a little old, so I was hoping that was the reason. So I also bought a new battery. Once I was finally able to take it out this spring it started right up and was running great. I noticed it was leaking gas out of the carbs so I rebuilt those and took care of the leak. However, throughout all this the battery would die from time to time. So I took it for another ride and noticed cylinder 3 was not running all of the sudden. So I started taking a closer look at the electrical system thinking this all might be related. Tested a few things and took it for a couple more rides. Sometimes it rides fine with no issues, but sometimes the charging system isn't working and sometimes it is. So after all this I'm not really sure where the problem is. This might be unrelated, but I thought it might be worth mentioning that the ignition cutoff switch doesn't work either.

So if anyone recognizes these problems, I would appreciate any and all advice.

Thanks!

[TwoTired]

It's going to cost a lot if you just replace parts that you have suspicion of, without active test results.
Batteries can be tested, usually for free at a battery supplier.  Testing will tell if the battery needs replacing or simply a recharge required.

That is the first step in charging system diagnosis, using a fully charged known good battery.  Then it is a matter of using a voltmeter to determine what RPM is needed to raise the voltage of the battery.

Your battery will normally not charge during periods of idle as the alternator can only make one third of peak capacity at that speed, and this naturally drains the battery.  Don't run the engine fast enough and eventually the battery can't make the ignition system spark the plugs.

The voltmeter vs RPM test will inform whether your charging system is working or needs further attention.  Report those numbers.

Cheers,

[69cb750]

but sometimes the charging system isn't working and sometimes it is

You need a volt meter.
Connect volt meter to battery, go for ride, watch volt meter.
12 volt to 12.5 volt bike is running off battery,not charging.
13 to 14 volts charging system is working.
We could guess wildly, having facts will help.

[Scott S]

 When you say ignition cutoff switch,  do you mean the kill switch on the RH control or the actual keyed ignition switch?
 This could be a hint.

[mkmob]

Sorry, I should have been more clear. When I said I had done some testing I meant that I had used a voltmeter and sometimes the charging system is working, but sometimes it isn't. I also tested the battery and I know that it's good.

I was talking about the kill switch. Whether the engine is running or not, the kill switch doesn't seem to do anything. I might just try cleaning some of the connectors and looking for any corrosion. On the surface it all seems fine, but I haven't gotten in close yet. I'm hoping that it's something simple, but that's probably just wishful thinking.

Anyway, thanks to everyone for all the advice thus far. I'll post here if I make any progress.

[TwoTired]

Normally the "kill switch" or OFF-RUN-OFF switch routes power to the coils in RUN position.  So, it has either been bypassed or you have a switch that is not stock.

We mostly know bikes in stock configuration.  If your bike has been attacked by modifiers, we can help less. The bike works well in stock configuration.

Cheers,

[mkmob]

So I was able to get the charging system working. Seems that the issue was just a result of old wiring. It still seems to be underpowered and when I tested it with a temperature guage, cylinder 3 is running a little cold. Sometimes it warms up after a while, but even so it just doesn't seem to have as much power as it should.

I'm going to try a few more things and see what I can figure out. I had decided to sell the bike and wanted to get it running good without needing to put too much more work into it. However, depending on how stubborn it's being I might just sell it as is.

[RustyF]

I recently had similar issues on my 550.  What are the numbers on the volt meter on the battery 1) with the bike off, 2) at idle, 3 at 4,000 rpm?   What does the the #3 plug look like?  While you have out start the bike and see if it is firing consistently.  Rule out the charging, then ignition systems.  I had a bad voltage regulator and installed a Rick's solid state unit to solve that part of my problem.  Then I cleaned and reset the float levels, got it running, set the pilots then vac synced the carbs.