Battery? Alternator? Starter? Ugh.....help please

xcb750x

So I have a 79 cb750 and I am looking for a few basic places to begin to troubleshoot this damn problem I have.
The bike will start, even after sitting for a while. In fact it starts up quickly and runs and idles fine. However, if I shut it down, either on the first or second shut off the bike will not start. By not starting I mean no juice, no turnover. It sounds like the battery just totally dies. Even after the bike has been running for a while. However, it seems as if the battery is still holding a solid charge. You can also hear the click, click...of what I think is the ignition.
No juice though....
I know there is a chance the battery is f-ed, but this will have been the second battery this year. So I know there is also something else at work here.
Any help would be appreciated. I'm rebuilding a 77 Suzuki and a 76 Harley, but this Honda I've never really done any serious wrenching on as it is a really strong runner....WHEN SHE IS RUNNING!
thanks

fxray · Posted: Mon Nov 14, 2011 4:26 pm Post subject:

I'm not familiar with the electrical system on your bike, but it sounds like you may have a bad starter relay switch. I had to put one on my 92 Harley last year, and a friend told me he had the same problem on his early 80's Wing. Take a look at your wiring diagram. Mine was an intermittent problem, and it always happened at the most inconvenient moment. Although the first one lasted over 20 years, the replacement has recently started to act up on occasion. I have a new one for it, but have not put it in yet. I know just where to rap my fist on the side cover to jar it loose and make it work.

Good luck.

BudW · Posted: Mon Nov 14, 2011 7:13 pm Post subject:

Check the battery voltage when in the no start condition, this will help to rule out the battery. Check and recheck all connections between the battery and the starter, don't overlook the ground connections.

Check the charging voltage also as it sounds like you might be cooking the battery, if the battery gets overcharged the plates get damaged. When this happens the battery will show good voltage at first but will deplete rapidly when you hit the starter button. Once depleted it will have nothing for a restart until it rests for a little while and the voltage will come back up and you can start the bike again

fasterspider · Posted: Mon Nov 14, 2011 7:16 pm Post subject:

Go to www.cb750c.com and then to the welcome forum and read the thread genesound went through a lot of trouble to write that thoroughly explains how to test each componenet for your bikes charging system.

I think you might have a bad solenoid though, pretty easy fix and if you are smart you will buy a 91 or newer CBR solenoid with a modern fuse built in instead of that caveman POS Honda use to put in there 32+ years ago. Check eBay for the solenoid with a BIN, that is where I buy mine.

midlifechoppers · Posted: Sun Dec 25, 2011 10:04 pm Post subject:

After starting a bike, it takes about 45 minutes of run time to recharge to previous battery state. If you have a weak battery, you don't have enough juice for another sequential start. Problem can be magified if your charging system isn't working fully. Will take longer to recharge. I'd check battery condition first then your charging system. If the battery is weak you're charging system really can't be assessed. If you have a good battery, you should be seeing about 13.5V after the regulator during charging.