Topic: 550 not idling, could battery be culprit?

[asbissonnette]

Hey everyone, it's that season again, so you'll probably be seeing my name popping up here as I try to get my 1975 CB550 running again.

So ever since getting this bike, last spring, I have had trouble starting the bike and letting it idle. It only wants to stay alive around 2800rpms. After driving for a while and the engine has had ample time to warm up, I can drop the idle to just above 2000, but no lower.

Over the course of my time owning it, I have torn apart and cleaned the carbs probably 6 times and have verified that there is no dirt coming from inside the tank. I know dirty or clogged carbs are not the issue.

I replaced the o-rings on the main jets and float needle jets.

Carbs are bench and vacuum synced, or at least as synced as I can get them due to the poor, inconsistent idle.

PO put straight exhaust pipes, but didn't re-jet.

The one problem I know of for sure is the battery is pretty bad and doesn't hold a charge. I can kickstart the bike after sitting on the charger overnight. But unless it has been sitting on the trickle charger, it doesn't want to start. The bike does kickstart pretty easily after I have been driving for a while though. So needless to say, I need a new battery.

Could the bad battery also be causing the bike to not idle properly also? It seems unlikely, but I'm sort of running out of options.

[vincentvega]

If you take the battery out and take it to a parts store they will often be able to test and charge it for you at no cost, I just had that done for my battery at Canadian Tire. That being said new battery's aren't expensive and you need a good charge for your bike to run properly.

There are lots of other causes that could impact a bad idle but I'd get the known bad battery issue resolved and see what happens.

Also check your owners manual and make sure you are operating the choke correctly, you might think it's off when it is actually on.

[TwoTired]

Could the bad battery also be causing the bike to not idle properly also?

Yes.
The 150W peak alternator only makes about 50 Watts at idle RPM, more when revved, of course.
However, when the lights are on, the bike uses about 120 watts.  What the alternator doesn't make, must be offset/supplied by battery power, which if the battery is flat or bad, is unavailable.  So, the voltage falls low enough to prevent spark and then silence.

You should be able to observe this with a voltmeter.  But, I'd say you need a good battery, even if you just want to check the charging system.

[Bailgang]

Could the bad battery also be causing the bike to not idle properly also?

Yes.
The 150W peak alternator only makes about 50 Watts at idle RPM, more when revved, of course.
However, when the lights are on, the bike uses about 120 watts.  What the alternator doesn't make, must be offset/supplied by battery power, which if the battery is flat or bad, is unavailable.  So, the voltage falls low enough to prevent spark and then silence.

You should be able to observe this with a voltmeter.  But, I'd say you need a good battery, even if you just want to check the charging system.

+1
Years ago when I first got my 550 together and running (and before I knew better) it was sometimes hard to start and when it did it didn't idle very well. One time I had a batt charger on it and it started right up and idled just fine but the instant I removed the charger it idled like crap again. From that point on I made sure the battery was in good shape and fully charged.

[asbissonnette]

Thank you for that answer. Just what I wanted to hear (ie numbers and logical explanation). Yes, I will get that battery swapped out soon. Thanks for the help!

Could the bad battery also be causing the bike to not idle properly also?

Yes.
The 150W peak alternator only makes about 50 Watts at idle RPM, more when revved, of course.
However, when the lights are on, the bike uses about 120 watts.  What the alternator doesn't make, must be offset/supplied by battery power, which if the battery is flat or bad, is unavailable.  So, the voltage falls low enough to prevent spark and then silence.

You should be able to observe this with a voltmeter.  But, I'd say you need a good battery, even if you just want to check the charging system.

[Duanob]

Spend the extra money and get a gel battery. I've gone through regular batteries about one per year now. They just don't seem to last very long. I'm on my second year of a gel battery and it still has plenty of juice. I haven't had to charge it yet.

[TwoTired]

Spend the extra money and get a gel battery. I've gone through regular batteries about one per year now. They just don't seem to last very long. I'm on my second year of a gel battery and it still has plenty of juice. I haven't had to charge it yet.

Don't you mean an AGM battery?    (Absorbed Glass Mat)

Gel electrolyte batteries aren't so good for starting battery use because the electrolyte has very poor mobility.

[Deltarider]

I've gone through regular batteries about one per year now.

I've done six years (twice) with original Yuasa's. The cheapies last around 4 years. Are you sure you treat them well and they're not on a charger/tender all of the time?