Voltage Regulator & High RPM's?
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LX50 4V
Joined: 18 Oct 2019
Posts: 22

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.
Hooked
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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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The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
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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
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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
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Posts: 22

Sat Nov 30, 2019 7:40 am quote
I have a basic multimeter (without continuity feature). Iím 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? Youíll know your cables are messed up if when you disconnect them your RPMís 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 12ís 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? Youíll know your cables are messed up if when you disconnect them your RPMís can go lower.
.
Single cable, no carb warmer.
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LX50 4V
Joined: 18 Oct 2019
Posts: 22

Sun Dec 08, 2019 2:58 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? Youíll know your cables are messed up if when you disconnect them your RPMís 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 12ís at rest and 13-14 charging. Report back what youre getting.
OK. Got some readings and discovered something about the carb.

Here are some readings;

READINGS 12/08/2019
Battery (not running) = 12.7V
Battery (running with high RPM) = 14.1V

Headlight Bulb readings (running):
High beam brown wire = 9.8V
Low beam purple wire = 7.7V
[Noticed recently installed new headlight bulb had exploded - broken glass in headlight lens area]

See next post reply for carb discovery.
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Sun Dec 08, 2019 4:26 pm quote
peacemakercc wrote:
Here are some readings;

READINGS 12/08/2019
Battery (not running) = 12.7V
Battery (running with high RPM) = 14.1V
So the DC bits are OK.
Quote:
Headlight Bulb readings (running):
High beam brown wire = 9.8V
Low beam purple wire = 7.7V
[Noticed recently installed new headlight bulb had exploded - broken glass in headlight lens area]

Are you sure you measured AC volts? Those readings look suspiciously like the multimeter was still set on DC measurement...
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LX50 4V
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Sun Dec 08, 2019 4:30 pm quote
Carburetor Discovery.

I've been mixing issues in this post. One of the issues was high RPM's. This high RPM issue kind of happened overnight. There is no throttle cable issue. I've adjusted the idle screw all the way out. Still high RPM's. So when I just went poking around, I decided to manually mess with the section that rotates (throttle control?) when the throttle is applied. If I put some pressure on it to force it further in the direction of lower idle, it will actually reach the right idle speed range. When I take the pressure off, the RPM's go back up
It's like the piece (throttle control?) won't rest fully in its lowest position allowing me to use the idle speed screw to fine tune the final speed. As you can see in the video, the idle speed screw is out past its limit already.

At least now I think I can separate the high RPM's issue and the idle speed into 2 separate problems.

Video:
Thoughts?
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LX50 4V
Joined: 18 Oct 2019
Posts: 22

Sun Dec 08, 2019 4:33 pm quote
jimc wrote:
peacemakercc wrote:
Here are some readings;

READINGS 12/08/2019
Battery (not running) = 12.7V
Battery (running with high RPM) = 14.1V
So the DC bits are OK.
Quote:
Headlight Bulb readings (running):
High beam brown wire = 9.8V
Low beam purple wire = 7.7V
[Noticed recently installed new headlight bulb had exploded - broken glass in headlight lens area]

Are you sure you measured AC volts? Those readings look suspiciously like the multimeter was still set on DC measurement...
Sorry but the meter I used is auto-ranging and auto select of AC & DC. I have another meter where I might be able to hand select AC (don't remember). Sorry but it's hard to get time to work on it, so my responses may not be prompt.
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Sun Dec 08, 2019 5:34 pm quote
High idle sounds like an air leak around the inlet manifold. They can crack!
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LX50 4V
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Sun Dec 08, 2019 9:11 pm quote
jimc wrote:
High idle sounds like an air leak around the inlet manifold. They can crack!
I sprayed starter fluid all around the area. No raise in RPM's. That tells me there's no air or vacuum leak.
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Sun Dec 08, 2019 11:25 pm quote
The throttle cable or grip is binding up somewhere.
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Mon Dec 09, 2019 6:49 am quote
Motovista wrote:
The throttle cable or grip is binding up somewhere.
+1, itís gotta be in the cable or throttle grip
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LX50 4V
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Mon Dec 09, 2019 6:50 am quote
Motovista wrote:
The throttle cable or grip is binding up somewhere.
Although I've quick-checked that, I'll give it a deeper check. If it's not bound, maybe there's a way to give it more slack?
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Mon Dec 09, 2019 9:11 am quote
The throttle cable is super simple. All the handlebar side does is retract it. The rest of the action happens in the carb, with a spring to return the throttle to its lowest point, a slide in the carb that retracts the needle from the jet and lets the fuel pass through, and a notch that engages the idle speed screw to allow the throttle to rest ever-so-much higher than the low point when the throttle is let go.

Maybe the spring is improperly seated in the tube (it can go flying, hold onto the screw cap carefully as youíre unthreading it)...maybe the cable end isnít fully engaged in the slide and is binding on the side of the carb...maybe the needle is bent and binding up in the chamber or not quite engaging in the jet....
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LX50 4V
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Mon Dec 09, 2019 6:56 pm quote
Juan_ORhea wrote:
The throttle cable is super simple. All the handlebar side does is retract it. The rest of the action happens in the carb, with a spring to return the throttle to its lowest point, a slide in the carb that retracts the needle from the jet and lets the fuel pass through, and a notch that engages the idle speed screw to allow the throttle to rest ever-so-much higher than the low point when the throttle is let go.

Maybe the spring is improperly seated in the tube (it can go flying, hold onto the screw cap carefully as youíre unthreading it)...maybe the cable end isnít fully engaged in the slide and is binding on the side of the carb...maybe the needle is bent and binding up in the chamber or not quite engaging in the jet....
I see a spring on the outside of the carb on the passenger side. It's on the thing the throttle cable pulls. When. The throttle cable is disengaged, the spring-loaded mechanism does not come back far enough to let the idle relax. If I take that mechanism and push on it a little bit in that direction of low idle, the idle will lower down. I noticed there are some locking nuts on the throttle cable casing end. Was thinking about loosening those in trying to move the casing in the right direction for lower . Unfortunately I can't get at this as often as I would like. It seems like every few days I have another chance to try a small something. And it's all being done on the fly in the parking lot..
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Mon Dec 09, 2019 7:09 pm quote
Sounds like youíre on the right track - and that the parts on the Vespa 50 carb are located a little differently from the 150 carb that I was referring to. But itís the same concept and isnít difficult to understand by inspection.
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