electrical issues

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electrical issues

Postby RocketMan » Wed May 06, 2015 5:08 am

got a question on a strange electrical issue I'm having with my 125. I put a small LED volt meter on it and every so often while at idle the meter will blink out very momentarily for just a split second then come back on. Its wired directly to the battery and it only happens when the bike is running and so far I've only seen it happen at idle but its kind of hard to watch it and drive at the same time so can't say for sure it doesn't happen at speed. My question is, with the meter wired directly to the battery is there anything that could happen with the electrical system, charging circuit or otherwise that could cause it to momentarily register 0 voltage at the battery, other than the meter being bad? It would seem to me that even if you lost output from the alternator or had a short somewhere beyond the battery all that would happen is that the battery voltage would drop to its non-charging voltage. I've checked the wiring to the meter and all connections are tight and wiring is all new. No matter how much I jiggle the connections the meter does not show the same symptoms.

I installed it due to the fact that sometimes when accelerating hard the bike will lose power and hesitate like what would happen if the carb bowl ran dry due to the float being set wrong and it always recovers as soon as I back off on the throttle and then accelerate more moderately. I've pretty much ruled out the carb as being the issue though and noticed that having an extra electrical load with cause this to happen like when the blinkers are working or headlight on which is why I think its electrical in nature rather than carb related. The electrical system on the bike is very rudimentary, no voltage regulator just a four diode rectifier from stator to battery. problem is I can't really pay attention to the meter when it happens cause, well, I'm paying attention to the road and traffic and the meter can be hard to read in bright sunlight. Really need to ride it some evening when I can really see the meter display but with a 6 volt lighting system I don't want to caught in full night time! :D

Any ideas on either issue?

RM
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Re: electrical issues

Postby jskene » Wed May 06, 2015 1:53 pm

If the blinking voltmeter and the loss of engine power happen simultaneously I'd say there was an intermittent short circuit somewhere in the electrical system. If it's not simultaneous, then the meter is likely at fault.
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Re: electrical issues

Postby RocketMan » Wed May 06, 2015 5:56 pm

The problem is I can't confirm that and I can't recreate the problem in the garage, it only seems to happen under load when in motion. The blinking of the meter only seems to happen at idle (as far as I can tell) and the bike rarely ever stalls or acts up at idle and revving it at a standstill produces no intermittent shutting off of the meter or misfiring. its only under load, the harder I accelerate the more prone it is do this but not always. I can take a long ride like when I went down to Jim's or to Old town Alex from Woodbridge and have no issues at all. The only thing I can get it to do while just sitting is hitting around 5000 RPM at which point the blinkers go bonkers, then settle down at higher or lower rev's. The meter may blink out when this happens but as I said I can't really pay attention to it while moving and when I do have a chance to check it the issue is gone.
So again could a short in the system cause a meter attached to the battery show 0 voltage even when the battery is good?
I am planning no moving the connections to the rectifier output and see it that produces the same results, seem to me it should since the wires go directly to the battery.
I have replaced the stator and diode diode is new the stator used but seems to read proper voltages per the manual. Blinker is also new. Wondering now if maybe I should replace the capacitor, I do have a new one, if that might cause the loss of power under load and will start going thru all the connections. Most I have checked so far seem firm and pretty clean for a 40 year old bike. Ignition switch is also new and all blinker bulbs match in wattage as per manual.

RM
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Re: electrical issues

Postby dcgsrider » Thu May 07, 2015 2:28 pm

Just a guess...but several of symptoms look like what happened when the voltage regulator started going bad on my 2000 SV 650 and my 1994 VFR.

The SV 650's finally gave up for good in Rock Creek Park, the speedo and tach dials went all wonky, then dropped to zero and the bike just stopped. Luckily, it failed by delivering too low a voltage, not too high. That's when things get fried.

I had a Honda VFR for many years and put nearly 100k miles on it. The mid-90s model years were notorious for having fragile rectifier/regulators that could not properly dissipate heat. I put a voltmeter on the bike. I limped home from a New England trip with one headlight to keep the voltage up. Just like the SV 650, that one also failed by delivering too low a voltage. So, I would say if you're experiencing low voltage intermittently, make sure the regulator is not going south.

(BTW, try getting a tow when all the driver has is a GPS and there's no "street address" to enter because, well, you're in a park.)
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