Author Topic: CB750K4 -bike dies at traffic lights -update - battery? -UPDATE 17/6/08 (Read 2175 times)

andy750 · « **on:** June 12, 2008, 05:03:25 AM »

Bike - CB750K4 - stock
Battery - AGM battery (1.5 yrs old)

Last night I found my starter button gave up (but still engages as lights dim when pressed). Then coming home the bike would die at lights and had to be kicked started to get going again...then die, then kick again...until I had to switch off the headlights to get it to start on kick and keep going. Once it was going it was ok (not perfect but ok), and the indicator lights were verrrrry slow to come on and so were more or less useless for indicating direction. Idle was all over the place. Headlight was dim-ish.

I think my short commute to work in recent high temps has killed the battery. Checked battery terminal last night and they were solid. Anyone agree that its likely the battery? Just looking for a second opinion.

cheers
Andy

bender01 · « **Reply #1 on:** June 12, 2008, 05:15:41 AM »

Normal batteriies last 3- 4 years if used often like yours so maybe. You dont have a dyna or something electric ignition? I dont remember my 75 550 dimming when the starter was pushed but when the battery died it was quick without warning.

andy750 · « **Reply #2 on:** June 12, 2008, 05:26:33 AM »

Yes it has a Dyna S - had it for 7 yrs now. The bike kicks over ok so I dont think the Dyna is the issue.

cheers
Andy

bender01 · « **Reply #3 on:** June 12, 2008, 06:22:31 AM »

I just think the electric ignition reqiures more juice is all. Did you have to keep the rpms up for it not to die out?

Gordon · « **Reply #4 on:** June 12, 2008, 06:27:42 AM »

Yes, your battery is running out of juice. What you need to figure out is why. I don't think the Dyna-S has much to do with it as a 750 charging system in good working condition can easily keep up with the slight extra power consumption. You need to check with a multimeter to see if your charging system is working.

750K2 · « **Reply #5 on:** June 12, 2008, 06:36:48 AM »

andy - btw, happy birthday! ok, on to the battery. i'll lend you my amp clamp so you can see if the charging system is working. sounds to me like you're running off the battery and not feeding it enough juice to keep up with the current draw. since your bike has run consistantly in the past and the battery isn't that old, i'd head directly and forthwith to the charging system. i've learned the hard way (with my boat) that you can only run a certain distance off the batteries if they're not getting a recharge from the alternator.
but let's say it's not the charging system. with the amp clamp device you'll be able to loop it over any wire you wish and determine the current draw at any rpm setting. if there happens to be a ground or short you'll know soon enough.
frank

andy750 · « **Reply #6 on:** June 15, 2008, 03:59:38 PM »

I changed my K4 AGM battery for my K2 AGM battery and the CB750K4 fired right up! So...has the 1.5 year old AGM battery died (seems odd - anyone have experience of AGM battries not lasting?), or something else is causing the battery to lose charge. Trip to NY state is in 6 days!! Hopefully the K2 battery will suffice.

cheers
Andy

Patrick · « **Reply #7 on:** June 15, 2008, 04:19:55 PM »

If it were my bike, Andy, I would put a charge on the battery to see if it would hold one and then check out the charging system. Many small things can go unexpectantly wrong with the charging system on these old bikes. Most of those things have happened my my bikes. I unnecessarily replaced batteries a couple of time just to find out they weren't at fault. It doesn't take that much time to make sure the bike is charging right and most problems can be fixed without ordering any parts.

Just my humble opinion.

Patrick

Gordon · « **Reply #8 on:** June 15, 2008, 07:04:45 PM »

Yeah, you really should make sure your charging system is working properly before taking off on a road trip. I might just be the battery, and it's easy to test.

In response to your question about problems with AGM batteries: It may have just been a fluke, but I put one in my 750 that went kaput after only a few months. And it didn't just slowly lose it's charge either. It went from fine one evening to completely dead the next morning, and wouldn't take a charge again after that.

andy750 · « **Reply #9 on:** June 15, 2008, 07:23:57 PM »

Thanks for the input Patrick and Gordon and of course you are both correct. I wasnt sure about putting the AGM battery on charge (slow charge) - is it possible to recharge an AGM? Unsure on that one. I was trying this afternoon but maybe didnt leave it long enough....

BTW what is the best way to check the rectifier? regulator? Never had to do this before....

Cheers
Andy

Patrick · « **Reply #10 on:** June 15, 2008, 07:39:42 PM »

This sounds like a job for TwoTired.

First, though, charge your battery, start the bike and put a multimeter across the battery while the bike is running. If the charging system is working correctly you should show 14 volts or more charging the battery over 4,000 rpm. If you are getting less, that's when the fun begins.

Patrick

Gordon · « **Reply #11 on:** June 15, 2008, 07:55:18 PM »

Don't worry about the individual components of the charging system until you know that there's a problem. Just test the voltage while it's running, like Patrick said, and see what happens.

Raul CB750K1 · « **Reply #12 on:** June 16, 2008, 01:54:42 AM »

I'm having a similar issue with my Sanglas bike -there is an open thread in the "other bikes" forum-. It seems as a charging issue, but you need some instruments to measure voltage and current while driving -or, at least, while revving the engine-.

andy750 · « **Reply #13 on:** June 16, 2008, 04:32:09 AM »

Quote from: Gordon on June 15, 2008, 07:55:18 PM

Don't worry about the individual components of the charging system until you know that there's a problem. Just test the voltage while it's running, like Patrick said, and see what happens.

Will do. Borrowing a multimeter tonight so will keep this thread updated as testing proceeds.

Thanks all,
Andy

Bodi · « **Reply #14 on:** June 16, 2008, 07:37:48 AM »

Of course you can charge an AGM battery. Just avoid high amp chargers, 1.5A is probably maximum. Once charges, start the bike with the kick starter and check battery voltage while running. Voltage should get above 14V with the revs over 2K or so. If not, try with the headlight disconnected.
The 750 has a fairly strong alternator but with a Dyna, 3 ohm coils, and a 55W H4 headlight... marginal. If you have all that then any reduction in alternator efficiency will be trouble. The usual bandit is tired bullet connections in the harness, there are many threads here about rejuvenating these. There are a lot of threads on further testing too.
The regulator and rectifier are key to performance, any problem with them will kill charging power. An easy test is to pull the black and white wires off the regulator and just connect them together, this puts the alternator at full power and if you can't charge up to 14+V you have to look for why.

andy750 · « **Reply #15 on:** June 16, 2008, 08:29:10 AM »

Thanks for the input Bodi.

I currently have a Dyna S, stock CB900 coils with Dyna wires, iridium plugs and H4 55W headlight so I agree that some of the bullet connectors may need refreshing. As an afterthought the two wires coming from the harness and going to the front brake light switch came broke off recently and ends are unattached...I doubt this has anything to do with it but mention it in any case.

Anyway tonight will test the battery (the good AGM from the K2) in the K4 and see if there is still an issue. I will also try charging the "dead" AGM with my newly bought battery maintainer (1.5amp charge). Thanks Bodi for the test for the regulator - Ill try this if there is an issue with the battery.

**EDIT -I checked the Electrics FAQ and all the info one could want is in there....so Ive printed out all about multimeters, testing this and that (thanks Bodi for some good info from here as well). Now looking forward to it!! *****

many thanks
Andy

andy750 · « **Reply #16 on:** June 17, 2008, 04:26:06 AM »

This is the results of my battery test - I was using my other AGM battery that came out of a running K2 (that had just gone 300 miles the day before so should have been good) and was testing it in my K4 - the bike that "died" while riding home last week....

I was using the testing procedure detailed in the FAQ- Electric section (and as advised by the above posts - thanks guys!)

Voltage with power switched on (not running) - ~12.5V
with headlight on - ~12.2V
Engine running and held at 2500 rpm -~13.5V
Engine running and held at +4000 rpm ~ 14.7V

So according to the FAQ THIS AGM battery is fine and my regulator/rectifier also appear to be fine. So my conclusion is, the other AGM battery for whatever reason has drained/given up. I will recharge it AFTER my NY trip and see if it can hold charge again but for now I think Im good to go for the NY Adirondacks tour next week (well at least thats what I told the g/f who will be riding with me

).

Thanks for the help and for pointing me in the right direction.

cheers
Andy

azuredesign · « **Reply #17 on:** June 17, 2008, 04:44:35 AM »

Andy,
Do you think you should do the same test with the original battery, just to be sure?
Ben

Jerry Rxman Griffin aka MuthaF'er · « **Reply #18 on:** June 17, 2008, 09:20:18 AM »

Andy,

Now that you and Mike have the engines down pat you might have to move on to the fine instruction and guidance of Professor TT for the next phase of your career, the course is called "Don't electricals suck 101" ?!

If at this point you don't have a multimeter, don't borrow one - buy one. You can get a cheap pocket size one for $10 or so to take with you, which might be a good idea for peace of mind. AND I'll promise you that you WILL (not might) need one in the future. After all you have TWO SOHC4s.

Keep in mind that you can always pull the headlight fuse during the day to save some juice should you start to have a low voltage issue (at least on my F). One readily observable symptom is turn signal slowness at idle with the beeper not sounding right.

Have a great ride.

andy750 · « **Reply #19 on:** June 17, 2008, 09:50:16 AM »

Sage advice Jerry and of course you are correct. I will defer to your age old wisdom on this one.

Ill be posting an update with photos on our return! Here`s hoping the weather co-operates

We are camping for 90% of the trip!

Cheers
Andy

UnCrash · « **Reply #20 on:** June 17, 2008, 10:18:57 AM »

Have a safe trip Andy~! Best wishes for a dry ride.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #21 on:** June 17, 2008, 10:48:30 AM »

Andy,

I don't think it's age old , more like old age

Quote from: andy750 on June 17, 2008, 09:50:16 AM

Sage advice Jerry and of course you are correct. I will defer to your age old wisdom on this one.

Ill be posting an update with photos on our return! Here`s hoping the weather co-operates We are camping for 90% of the trip!

Cheers
Andy

mcpuffett · « **Reply #22 on:** June 18, 2008, 02:41:01 AM »

Hope you have a great trip Andy and the bike behaves

andy750 · « **Reply #23 on:** June 18, 2008, 04:18:40 AM »

Thanks guys! Last night i changed the front sprocket from 17 to 18-tooth for a more cruiser like ride on the highway. Oil/filter has been changed, tires are good, luggage is packed so...ready to go. Updates after the 29th

cheers
Andy

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Author Topic: CB750K4 -bike dies at traffic lights -update - battery? -UPDATE 17/6/08 (Read 2175 times)