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I recently acquired A 2010 LX50 4V that had been sitting a couple of years. Got it running for less than $2. That's the good part. Now little issues are coming up and I'm trying to address them. After function ok for a couple of weeks of short rides, the idle speed has gone way up practically overnight. When I now ride it I have to brake hard to stop. It's manageable but needs fixed. I can't seem to find any real info on an idle speed adjustment screw. It's not the throttle cable. That's fine.
Thank you for any insight.
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Your idle screw is the one in the first picture with the spring under it. To. get the idle set right get the engine warmed up and be sure that the enricher is closed. to do it properly you really need a tachometer, they are relatively cheap I use one like this https://www.amazon.com/Resettable-Inductive-Tachometer-Motorcycle-Snowmobile/dp/B01CR2IC2Q/ref=sr_1_5?crid=27LAVBENCPYX2&keywords=digital+tachometer+small+engine&qid=1571493967&sprefix=digital+tacho%2Caps%2C138&sr=8-5. turning the screw in will raise the RPM and out will lower it. The RPM's should be 1900-2000rpm. Be sure you have the correct setting on the Tachometer, they are for 2 and 4 stroke engines. The problem could also be an air leak that could be creating a lean condition. be sure all of the hose clamps are tight.
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Ok. Now the only problem with that screw is that it's already backed out all the way. That was the first thing I went for.

The vacuum leak sounds like a logical next idea, especially since the change happened overnight for no apparent reason.

So next, I'll start it and selectively shoot small bursts of starting fluid in different areas to listen for an RPM increase. I'm thinking that's how I'd find a vacuum leak hole. Make sense?
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So now I've started it and sprayed starting fluid around the whole greater carburetor area. No change whatsoever in RPM. So I'm guessing it's not a vacuum leak or idle speed screw.
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Could be a clogged jet, or malfunctioning electric choke (the part beneath the round black plastic cover in your first photo). If the choke isn't disengaging, it will affect the idle speed.
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thefakebecky wrote:
Could be a clogged jet, or malfunctioning electric choke (the part beneath the round black plastic cover in your first photo). If the choke isn't disengaging, it will affect the idle speed.
As for the jet, I'd recently checked the jets because it had been sitting. They were already clean and I cleaned again.

Thinking about the auto choke, is there a way to test that? I was thinking that if there was an issue like the choke being stuck on that it would run like most engines that have the choke on after serving its purpose, that it would just run poorly and act like it's flooding. ?

It'd be great to know if it can be tested. I'm not in a budgetary position to throw blind money.
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I haven't tried on an LX50 carb specifically, but on other similar setups, I've removed the choke but left it plugged it. Turn on ignition, and wait for it to heat up. You should be able to feel it get warm. Once it's at temp, the pin should move in or out (I don't remember the direction off the top of my head). It should move enough that you can see a difference in position.
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I found a site that mentions checking the auto choke. When cold, it's supposed to be in the retracted position. That's where it is.

Frustrating! Other ghosts are plaguing as well headlight bulb died. Replaced bulb, died again shortly after. Then the dashboard high beam indicator went out. gas guage not working. Frustrating trying to figure out a mystery on a zero budget with limited experience.
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Well, blowing out bulbs is a classic symptom of a failed regulator or stator. I would suggest investing in a cheap multimeter, about $10 from Harbor Freight, and taking some readings on the battery and the headlight power contacts while the engine is running at various speeds to better understand how the electrical system is doing. Unfortunately I can't see how that would affect the idle speed but it is confusing that you can't get that down. Usually it's simple to reduce throttle until the engine stalls. Are you certain the throttle in the carb is actually responding to the cable position?
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check to see if the air cleaner has decomposed and is missing large pieces. Also, assuming you got into the carburetor, check that the slide needle is going down into the hole and not hanging up.
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Ok on the air cleaner. Can check.

What is a slide needle?
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Juan_ORhea wrote:
Well, blowing out bulbs is a classic symptom of a failed regulator or stator. I would suggest investing in a cheap multimeter, about $10 from Harbor Freight, and taking some readings on the battery and the headlight power contacts while the engine is running at various speeds to better understand how the electrical system is doing. Unfortunately I can't see how that would affect the idle speed but it is confusing that you can't get that down. Usually it's simple to reduce throttle until the engine stalls. Are you certain the throttle in the carb is actually responding to the cable position?
I was hoping to only have this thread focused on one problem so as not to get too much confusion in one thread but I couldn't help but leak some more issues.

I have a basic multimeter. Not sure exactly how to apply it skillfully. But I'm all for taking direction.

The carburetor throttle cable seems to have zero issue.
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This project seems to be destined for frustration, with multiple things wrong, no experience, and no budget. Why did you decide to start this and how do you expect to address the issues? If the former owner failed to invest in whatever it took to keep this in good shape, the new owner is not going to be able to magically overcome that.
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Not looking for magic. The person I got it from didn't ever get around to registering after purchase. Then she got caught up in life and moving which led to it sitting for at least a year and a half. I got it from her through bartering.

Now that I've got it legal, I started on the can of worms. Got it running for less than $2. Then I replaced the battery, so I'm up to $42. Then I rode it around on several short runs within 1 mile. At that point I knew I at least had the front brake left to deal with.

Then on a night run to the store the headlight went out. Approximately the next startup or 2 after that the rpms went up. So, yes there are a few issues.

As far as repairs and experience, it's not that I'm completely inexperienced or an idiot. It's more that the budget is often very low and I do pretty well with guidance from those with more experience (which is why I'm here).

So the main topic I'm trying to cover on this post is high rpm. The rest of the issues on the checklist off hand are; headlight blowing, high beam indicator & fuel guage not working, front brake was gummed and clogged (now cleared but lost the banjo bolt - need to find another), transmission noise (but functioning fine). That's mostly it. Just trying to chip away. Considering the initial investment was about less than 8 hours of barter work, I'd say there's plenty of room left for this being a feasible pursuit. But, taking it somewhere to pay high shop fees? That'd probably out me at or above the category of worthwhile.
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Re: the high idle, I'd go back to the carb and air intake. If there's a leak or derestricted flow of fresh air, that would create a lean mix.

Re: the electrical gremlins, check the wiring harness near the battery. There are also. A couple of fuses in there as well. When I got my LX150, the PO had done a hack job with an oversized battery. That led to the shielding on some of the wiring getti worn through b/c of rubbing on the frame. That allowed for some corrosion, which created resistance (and heat), which led to fuses continually burning out, and then headlight, fuel gauge, and other dash lighting issues.

Re: transmission noise, it's probably worth opening up the CVT cover, making sure the belt, rollers, and clutch are in good shape. You also probably want to change the engine oil, filter, and gear oil while your at it.

I was in a similar situation when I got the LX150, with a long list of issues to address. Just take it one step at a time, and you'll get there.
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You're not going to get any better guidance on Vespa carbs, adjustments, and troubleshooting than these ScooterWest videos with Robot.

"https://www.youtube.com/watch?v=xoPVQCs919w"

"https://www.youtube.com/watch?v=QlXTE2bLWMI"

(Older carbs - less relevant but still interesting:)
"https://www.youtube.com/watch?v=h-wpPQ5nbHM"
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Thank you all for the understanding and great responses.

Although more than likely slowly, I'm going to sort through these. I like the electrical gremlins mention. Sounds just like my issue.
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The enricher might be the high RPM issue. On My S50 when I start it it revs at 4000rpm until the enricher closes. You can test it by pulling it from the carb and putting 12 v to it from the battery. Watch the plunger and see if it extends. If it doesn't it is probably bad. Now with the multimeter when the engine is running check the voltage going to the enricher it should be 12v I think.

The electric problems are possibly the voltage regulator. Put your multimeter on the negative and positive battery terminals and check the voltage. Then start the engine and slowly rev it up and see what you get. It should max in the 13.5-14VDC. If it goes much higher then your voltage regulator is bad and blowing bulbs. This should not be causing the high revving problem because the enricher gets power directly from the stator.
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Pinkscooter wrote:
The enricher might be the high RPM issue. On My S50 when I start it it revs at 4000rpm until the enricher closes. You can test it by pulling it from the carb and putting 12 v to it from the battery. Watch the plunger and see if it extends. If it doesn't it is probably bad. Now with the multimeter when the engine is running check the voltage going to the enricher it should be 12v I think.

The electric problems are possibly the voltage regulator. Put your multimeter on the negative and positive battery terminals and check the voltage. Then start the engine and slowly rev it up and see what you get. It should max in the 13.5-14VDC. If it goes much higher then your voltage regulator is bad and blowing bulbs. This should not be causing the high revving problem because the enricher gets power directly from the stator.
Enricher? Would that be the automatic choke? Not familiar with the word, Enricher.

Thank you for the simple way to diagnose the voltage regulator. Love the straightforward approach. It's funny that you mention slowly revving up the motor because I'm also having the idle issue. Lol. As soon as I start it, it zooms right up. Fortunately I can counter that a good amount by holding the rear brake. I'll just hold the brake then slowly release it.
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You may also have a small crack in the intake manifold, or a leaking gasket at the cylinder head. But it's probably the electric choke.
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FrankNBrew wrote:
You may also have a small crack in the intake manifold, or a leaking gasket at the cylinder head. But it's probably the electric choke.
With the engine running, I sprayed starter fluid all around the carburetor and general area. No change in RPM. I think that, unless I'm wrong, any vacuum or intake leaks would have resulted in an RPM surge.
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Another thing to check is to make sure the throttle isn't binding.
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FrankNBrew wrote:
Another thing to check is to make sure the throttle isn't binding.
Throttle is completely free of binding.
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