Battery (and bike) dying after 20 minutes or so...help!

I'm hoping maybe someone out there has had this problem: With a new and a freshly-charged battery (happened 2x) my 93 ST1100 starts and runs great until it starts sputtering like its running out of gas and finally dies completely - at which point the battery is totally dead. First time I took a chance it was the battery and replaced it - started and ran fine, but the next timne I went over about 20 minutes it did the exact same thing. This time I had to have it towed to my local dealer, where its been for 2 + weeks because they can't figure out (or recreate) the problem. Alternator is putting out 13.5 VDC, and seems to be working fine. Today they are going to run it longer to see if they can get it to die again, and maybe find the problem.

Has anyone out there had this problem with their ST? I really appreciate any advice. I usually do all my own work, but when it comes to electrical I tend to be pretty clueless.

Thanks.

Sounds to me like a ground issue, maybe loose ground somewhere so that the alternator is not running the system and instead bike ends up running off battery.
There is a way to check all connections for proper voltage, maybe John O. will come along and post it up as I believe he was the one that posted it.

13.5 V is not what you should be seeing from the alternator. Should be at least 14.5 V when engine revs are up. Could be either an alternator or VRR (voltage regulator/rectifier) fault, which wouldn't be that unusual for a 28 amp system of that age.

The Honda Service Manual shows the proper alternator and VRR tests. If your dealer is unfamiliar with this bike, or hasn't got the manual, they may not be of much help.

The 20 minutes make me wonder...
Even with no charge from alt/VRR at all, a fully charged battery should give <1 hour flight time...

There's a big 55A fuse near the battery (it's in a small black box overlying the battery). When I had a dead battery years ago, I jumped the bike with my car and unknowingly blew that fuse. I put a new battery in the bike and it ran fine, once, and then I had another dead battery. I saw the fuse in the black box which had broken (wish I had a pic of it), swapped it out for $3-4 and it's worked fine since. It might be worth a look.

BTW, my Honda Service manual says the Regulated Voltage should be 12.6v to 15.0 v @ 5,000RPM for the '91-'95 models..

AND, with the ignition switch OFF, there should be no more than 0.003 amps of battery leakage current. DISCONNECT the negative battery cable and bridge your ammeter between the negative battery cable and the negative battery terminal to make the measurement.

I bet yours is much higher than that. If it is, try disconnecting the VRR and see what it measures. The R/W wire from the VRR is connected to the 30 amp main fuse ( not a 55 amp alternator fuse that the newer models have ) that is connected to the positive battery terminal. My bet is on a defective VRR. A high current draw in any other circuit would blow a circuit fuse.

Have you checked the continuity between the three yellow wires?
https://www.st-owners.com/forums/showthread.php?49937-Need-Alternator-Help-93-Non-ABS&highlight=

Thanks for all the quick replies - this is very helpful! The bike is still in the shop - they took it for a short ride but couldn't recreate the problem. I will probably just pass the info on to them - its a Honda dealer so I assumed they were familiar with the bike, but maybe not. I don't want to get into an electrical problem that I can't fix. I had to have the bike towed, and don't really want to do that again. I'm already owing them for the diagnostic time, so they may as well finish the job. None of these suggestions should take very long.

Thanks again!

Thanks for this also - lots of good info.

>>> Have you checked the continuity between the three yellow wires?
https://www.st-owners.com/forums/show...ABS&highlight=

Erdoc48 said:

There's a big 55A fuse near the battery

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Not on a '93 model. That came with the 40 amp alternator on the post '95 models.

Bush said:

Not on a '93 model. That came with the 40 amp alternator on the post '95 models.

Click to expand...

I wasn't aware of that...thanks for the update.

ST1100Y said:

The 20 minutes make me wonder...
Even with no charge from alt/VRR at all, a fully charged battery should give <1 hour flight time...

Click to expand...

Did you mean greater than (>) one hour of flight time? Seems to me a fully charged battery should power the bike for more than an hour. A 93 1100 is running on carbs, so no constantly running fuel pump for fuel injection. The biggest load would be the lighting, ignition does not take that much juice.

SMSW said:

Seems to me a fully charged battery should power the bike for more than an hour.

Click to expand...

Not gonna happen... fuel pump, ignition, ECU, headlights (hard-wired on US spec), taillights, dash illu, brake light, turn-signals... and any additional draw from accessories...
On an EC-spec one can gain a bit by killing the headlights (saves 2x 55W) and run with position/marker only...

Been there twice...
On the prev '92 the stator connector went south (due to extensive washing by owner...), leading to meltdown of VRR & adjacent harness...
I did wonder why the headlight seemed a bit yellowish, but continued heading home, once in the city something dawned to me as Sony stereo went off/on in the rhythm of the turn-signals... ;-)
Switched off the LOW beams and continued, but like 10 min later the ignition failed... in total 45 to 50 minutes...

On the '94 the alternator shorted to ground on the way to the annual MOT (= instant total loss of all electrics), quickly pulled the stator-connector, turned off LOW beams and headed on, did the MOT procedures and rode back home; 20 minutes urban traffic each way, plus ~15 minutes MOT tests (incl emission test) and cranking the engine 3 times... so again about 50 minutes (would have been longer if I'd to start the engine only once...)

So the mentioned 20 minutes would indicate a serious leakage in the electrics...

ST1100Y said:

Not gonna happen...

Click to expand...

+1 on that. I was adding some LEDs marker lights and had to turn the ignition on and off over an hour almost two to check the wiring and connections. And to admire the lights. This probably wasn't a half-hour of on time. When I tried to start the bike all I got were lights and a clicky starter solenoid. But no spark for the engine. Run the ST on a total loss ignition system for an hour? No way.

A cool mod would be a new battery box that would hold a higher capacity battery.

Late chiming in... it could be as simple as the red main connector located near the battery... know problem.