Topic: Sudden Drastic Failure? ('81 CB650)

[Billy_Awesome]

Hello everyone,

I tried posting this a couple of hours ago, but I don't think it went through.  Apologies if I'm repeating myself.

I should start out by saying that I'm not a mechanic, and when I bought my bike, I had no real intention of becoming one.  Basic maintenance, sure -- fluids, air pressure, &c., but my understanding of the internal combustion engine doesn't go a whole heck of a lot further than "gas and air go in the top, smoke and noise come out the back," and I was more or less content to keep it that way.  I bought a motorcycle that was supposed to have been gone over from stem to stern, and as far as my limited ability to discern could tell, had been.  To anyone who suspects I might have paid a little extra for that peace of mind, you are correct.  A lot extra?  Oh, probably.

Recent events have made it fairly clear that "if I'd wanted something to take apart and put back together again, I'd have bought an Erector Set"-type thinking isn't going to fly with this particular machine, at least not within the budget I'm working with.  On the other hand, knowing as little as I do, and having turned as few wrenches as I have, I'm more than a little gunshy about trying something that'll do more harm than good.  Even the limited action I've taken seems to have moved the situation from bad to worse; calling my brother and asking him to pick the bike up and move it to Massachusetts for winter storage a few months early is probably the best idea I've had in a couple months. 

So disclaimer and swallowing of pride and excuse-making taken care of, I have a couple of questions, which are mainly for my general edification, but partly too to confirm my suspicions that I was royally ripped off when I bought the bike.

Question 1: Can an alternator suddenly fail?  If defining "suddenly" helps, I'd be talking either the course of three or four weeks, if my battery problems were due in any way to me not riding fast enough or for long enough to put back more juice than getting the bike started and warmed up took out, or a couple days, if I measure the time between problem-free riding and the first time I had to push it home.

Question 1(b): In the event of sudden alternator failure, would the stator or the rotor be the more likely culprit, or is there no way to tell?

Question 2: Do the carbs ever suddenly need to be resynched, seemingly out of nowhere, and without much if any warning?  "Sudden" in this case would be defined as maybe five days, two running and three sitting, or 15 miles?  If one were to do a bad job synching the carbs, would they be OK for a few months, and then go downhill within the timeframe I just mentioned?

Question 2(b): Would the sudden falling out of synch be preceded by a sudden chance in idle speed (from 1200 to 3500+ rpm), or caused by fiddling with the idle speed knob to bring it back down to normal?

My apologies if these are foolish questions, or a waste of anyone's time. I can try to provide more information if it makes any difference, though it wouldn't be particularly technical or well-informed.  I've searched the forum, and get things a little better now, but thought I'd ask just the same.  Maybe knowing a little better what's going on will make this seem like less of a fiasco, and me less of a damned fool.

Thanks,

-B

[tomkimberly]

Sorry to hear of your problems, but yes, stators fail without warning. Could be something as simple as needing new brushes and something as bad as needing a new stator and regulator.

I suspect your issues with the idle are systemmatic with your charging issues and not the syncing of the carbs. Address one issue at a time. My money is on the brushes need replacement.

Don't forget to recharge the battery!

Tom

[cb650]

Clean the tank and carbs.  Tank first and maybe the carbs will flush out.  Do a search on site about the 650 charging problems.  Many people have had them but all mine work fine.



                    Terry

[Billy_Awesome]

Thanks for letting me know.  If the stator can fail suddenly, then that opens the possibility that this was a case of bad luck and not a knowing swindle.  Restores my faith in humanity a bit, and shores up my wounded pride a little.  If the charging problems could be affecting the engine performance, that's reassuring, too, but like you say, I'll worry about one thing first, and then move to the next.

I did print of a bunch of posts from this forum, along with .pdfs of the owners' manual and a general Honda repair manual, plus some general cycle charging stuff from other websites, and tried to follow the directions, but got overwhelmed.  Not dragging so much information (some of it conflicting) out all at once probably would have helped, and thinking about it, I was pretty frantically grasping at anything that might get the bike back on the road before the season ended.  Now that the hope of that happening is effectively zero, and the bike is stored someplace safe where it can come apart and not have to be put back together again before the next rainstorm, I can step back and look at things more calmly and methodically.

I also took another look at my checklist of things that the previous owner said were done before I bought it, while carbs are on the list, the gastank isn't.  I never even got to ride far enough to need to refill it, so honestly I don't even know for sure how old or good the gas currently in it is, or what the tank looks like below the gas level.  It smells OK and there's nothing floating in it that I can see, but that's all I can really tell.  I'll take a look at that first if fixing the charging problem doesn't improve the way the engine runs.

Thanks for the advice and the reality check.  I still have a LOT to learn, it feels a whole lot less like the cluster!%@& it did before.  I really appreciate it.

-B

[750essess]

If your alternator failed ( most likely the rotor) then your idle will increase, because the load on the engine the alt created is now gone.

[Billy_Awesome]

If your alternator failed ( most likely the rotor) then your idle will increase, because the load on the engine the alt created is now gone.

Would that be because the rotor's no longer turning, or because the production of electricity itself puts a load on the engine (magnetic field or electrical resistance or something)?

Was fiddling with the idle control a bad idea, then, or didn't it make a difference?  I was a few miles from home when the idle speed suddenly took off.  Would it have been better to have ridden home with the engine racing, rather than pulling into a parking lot and trying to correct it?  What if I'd been further from home -- 10, 20, 30 miles, say?  Is is there any rule of thumb, as far as that goes?

Thanks,

-B

[jerrit1]

It would be because the load on the engine is gone.
Fiddling with the idle control was not a bad idea and it would not have been better to ride home with a racing engine.
If the bike runs and you can adjust the idle to get home safely then by all means...do it.
Repair the alternator and re-adjust the idle screw.

[dusterdude]

billy,nothin against my other brethren on here,but for your charging issues get a hold of two tired and let him school you thru this.good luck.

[Billy_Awesome]

I got to check on the bike over the Thanksgiving Holiday, and:

-The tank was full of crud, and will have to come off and be drained & cleaned.

-The carbs are also coming off and getting rebuilt, in part because of the goop in the tank, and in part because my brother trusts his own abilities more than he does the PO's mechanic's.  A bigger job than I'm up to tackling, but I'm going to try to be there to see it done.  Not sure whether that'll actually pan out or not, given schedules & locations.

-Started it up with a fresh charge on the battery.  It ran miserably, but had no charging problems whatsoever, at least in the couple minutes spent checking. 

So we're thinking either I was draining the battery to within an inch of its life every time I just tried to get the bike to start, and never managing to get up to speed enough to put it back, or the alternator's fine until it gets hot, and then fails, or possibly some combination of the two.  That issue's on the back burner for the time being, though, until the bike is actually capable of starting and idling.

Thanks again to everyone for their advice.  This is way easier to handle when approached calmly and step-by-step (and with someone who's sure he knows what he's doing heading up the project.

[UnCrash]

So we're thinking either I was draining the battery to within an inch of its life every time I just tried to get the bike to start, and never managing to get up to speed enough to put it back, or the alternator's fine until it gets hot, and then fails, or possibly some combination of the two.  That issue's on the back burner for the time being, though, until the bike is actually capable of starting and idling.

Hi Billy.

Starting and idling the bike will eventually kill the battery.  Most of the SOHC's need to be ridden above 3k rpm to get into the battery recharge range.  If you're idling the bike in your driveway, and restarting it multiple times to just hear it run because it's a new bike (been there - done that)  You're draining your battery and not recharging it.

All the best-

Ben

[BobbyR]

Your correct, do everything step by step. To check your charging system you need a simple voltmeter. If you have 13-14V at 3K your are ok at that engine temp. Ride her a bit till shes really warmed up and take another reading. You also have a regulator can can fail or just have plain corroded contacts. Carb synch will not kill the bike. I think many of us are used to low reving engines due to the overdrives in our cars so we tend to pick too high a gear for the speed we are traveling. I try to keep the motor above 3K when riding on all types of road. 

[mattcb350f]

Bobby's spot on, a simple volt meter will tell you if the alternator is producing power or not. When you do find out if it is or isn't, don't jump to conclusions as to what the culprit is if it turns out it's not. A single broken wire or loose connector can cause a charging failure, so you'll want to troubleshoot carefully before buying expensive parts.
I know cause'  I just found a loose connector causing the same problem on my Honda quad 

As for the irratic idle, like it's already been said, take it step buy step. You know there is crud in the fuel system so after that's been taken care of, try it again. Like the charging system, some simple things can also cause irratic idle like a sticky cable.

Good luck, Matt.