Voltage Regulator & High RPM's?
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LX50 4V
Joined: 18 Oct 2019
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Thu Nov 28, 2019 10:13 pm quote
Trying to slowly work through some issues on A 2010 LX50 4V.

I have some separate issues and I'm wondering if some are related. Without going in depth, I think my voltage regulator is bad (unconfirmed) based on a couple things. One is that it's blowing headlight bulbs. Another problem is that the RPM's are high. The idle screw is already out as far as it will go. The RPM issue happened about the same time as the headlight issue.

Is it possible, since there are electronic carburetor components, that a faulty voltage regulator would cause something electronic to make the RPM's rev higher, like with something electronic and carb-related receiving the wrong voltage? Hope that makes sense.
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Fri Nov 29, 2019 1:17 am quote
If it has an ECU it can be the cause.
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Fri Nov 29, 2019 10:09 am quote
It's easy enough to check the voltage regulator with a voltage meter. Also make sure all of the hoses and wires are connected properly. Those engines use lots of things to meter performance and the ECU does a lot of monitoring. Its possible you have an air leak or throttle cable issue causing the high idle
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LX50 4V
Joined: 18 Oct 2019
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Fri Nov 29, 2019 12:22 pm quote
What's an ECU and can it be tested?

The throttle cable is free. There are no air leaks. I sprayed ether around all the critical areas while it was running with zero change in idle.
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Fri Nov 29, 2019 5:51 pm quote
Buy a multimeter for around $10 from Harbor freight (or wherever) and check the voltages! This is this only way to diagnose some faults.
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Fri Nov 29, 2019 6:18 pm quote
Had a recent issue with a 50cc scoot (not a Vespa) that was blowing headlights and instrument panel bulbs, and acting erratically with high voltages (>17V) onto the battery at high RPMs on the stand.

The problem was eventually traced to a ground wire that was supposed to be attached to the regulator (rectifier) mounting bolt, but that had not been replaced properly by a previous owner or mechanic.

There is no substitute for a multimeter when trying to diagnose electrical problems!
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LX50 4V
Joined: 18 Oct 2019
Posts: 16

Sat Nov 30, 2019 7:38 am quote
Juan_ORhea wrote:
Had a recent issue with a 50cc scoot (not a Vespa) that was blowing headlights and instrument panel bulbs, and acting erratically with high voltages (>17V) onto the battery at high RPMs on the stand.

The problem was eventually traced to a ground wire that was supposed to be attached to the regulator (rectifier) mounting bolt, but that had not been replaced properly by a previous owner or mechanic.

There is no substitute for a multimeter when trying to diagnose electrical problems!
Sounds similar. Must check voltage at the battery. Thank you.
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LX50 4V
Joined: 18 Oct 2019
Posts: 16

Sat Nov 30, 2019 7:40 am quote
I have a basic multimeter (without continuity feature). Im just not very experienced at diagnostics. I can at least test little things like return voltage to the battery. Any other multimeter suggestions greatly appreciated. Thanks
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Sat Nov 30, 2019 9:03 am quote
Most multimeters can measure resistance (Ohms) even if they don't have an audible "continuity" beeper. Set the meter on the lowest Ohms range (usually "200"). Then you can read continuity, about zero Ohms. Remember the leads will add about 3 to 4 ohms.

Last edited by JKJ-FZ6 on Sat Nov 30, 2019 7:25 pm; edited 1 time in total
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Sat Nov 30, 2019 2:09 pm quote
The only electrical components on an LX carburetor should just be the electronic choke (enricher) and a carb warmer. If the choke failed, the motor would probably be running like shit since its too rich.

Did you mess with the carb? Rebuild or possibly mess with the throttle cables at the carb OR below the hand grip? Youll know your cables are messed up if when you disconnect them your RPMs can go lower.

As far as the voltage regulator goes, definitely purchase a multimeter. One that measures both AC and DC voltage. Make sure all your ground wires are connected and secure, and then disconnect the wires from the bulb. Take a photo of it with your phone first so you know which wires go where. Turn your meter to AC voltage and measure at the wires with the engine running. It should be clipped around 12V full revs. in a perfect world which we know youre not having since youre popping bulbs. Report back what value youre finding.

Switch your meter to DC voltage and then measure the battery voltage at the terminals. Should be high 12s at rest and 13-14 charging. Report back what youre getting.
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Sat Nov 30, 2019 7:16 pm quote
MJRally wrote:
The only electrical components on an LX carburetor should just be the electronic choke (enricher) and a carb warmer. If the choke failed, the motor would probably be running like shit since its too rich.

Did you mess with the carb? Rebuild or possibly mess with the throttle cables at the carb OR below the hand grip? Youll know your cables are messed up if when you disconnect them your RPMs can go lower.
.
Single cable, no carb warmer.
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