2013 KYMCO Downtown 300i hesitation while throttling issue

[CROSSBOLT]

I do believe the vent valve is buried below the gas tank behind the radiator. At the very least it will take literally HOURS to get to it. I even was sent a replacement valve but sent it back when I saw how much plastic body panels had to be removed to get at it. That's when I drilled a hole in the cap.

[scootermaven]

I do believe the vent valve is buried below the gas tank behind the radiator. At the very least it will take literally HOURS to get to it. I even was sent a replacement valve but sent it back when I saw how much plastic body panels had to be removed to get at it. That's when I drilled a hole in the cap.

 

Yeah, getting to that vent doesn't sound fun at all.  I don't blame you for sending the part back and opting to just vent the cap yourself.  If this is a common problem with these scoots, sure wish somebody would make a video of the cap venting mod and put it up on YouTube.  Anyway, I have to go get a key made at the local key shop so I have an extra key for the scoot, as I don't have the extra key for it at my current location.  I'll be back in-touch soon afterwards to see if that is even the issue.  Thanks, Karl.  I really appreciate your help with this.

[CROSSBOLT]

It IS a common problem! Genuine Buddy forum called it "The Stall of Shame" and the fix was to vent the gas cap. It effects every brand and every model sooner or later. Very few none at all.

[scootermaven]

It IS a common problem! Genuine Buddy forum called it "The Stall of Shame" and the fix was to vent the gas cap. It effects every brand and every model sooner or later. Very few none at all.

Well, don't think that's the problem with mine, Karl.  It was worth a try, though.  I turned the key on the cap to loosen it while having the hesitation issue and that didn't seem to have an effect.  I left it loose for about 10 minutes while riding and still the same hesitation.  I don't know if this helps or not, but when I got the scooter, I drained-out a tad over 6 ounces of engine oil because someone had over-filled it apparently.  Could the too much oil situation have caused any problems maybe???  Thanks!

[scootermaven]

If cap is vented, hole should be clear.

According to "Crossbolt", fuel cap is not vented.  Perhaps the tank is vented elsewhere.  The hesitation problem persist with the fuel cap loose though, so that likely rules-out that being the issue.

I'm on my 2nd tank with fuel system cleaner mixed in the tank, but no improvement to this point.  I put about a 1/2 ounce of Lucas Tune Up In A Bottle (Upper Cylinder Lubricant and Injector Cleaner) per each full tank. 

I was telling "Crossbolt" that there was too much oil in the scooter when I first got it, so I drained-out about 6 ounces to get it to the proper level on the dip stick.  So, I am wondering if that situation may have contributed to the hesitation issue in some way.  There was no oil in the air box and the filter element is clean.  The plugged drain tube connected to the air box didn't have much oil in it either, but I drained-out what little there was in the tube.

Thanks, John!

[mousejunks]

You need to remove the seat and look at the engine.

Air flow - gaps in the throttle body, breather hoses around the air box, oil tube below the air intake. They can cause vacuum leaks or allow dirt in and mess up the airflow sensor.
Spark plug - remove it and inspect the plug tip. Allow check the spark plug boot for corrosion.
Fuel - run some injector cleaner and see if it helps.
Connectors - unplug all the connectors on the throttle body and reconnect.

[CROSSBOLT]

The tank IS vented elsewhere! There should be a fuel system diagram sticker at the rear of the seat tub that shows it is vented through the vacuum valve to the charcoal can. Your test with the gas cap pretty well rules out the stuck vent valve theory so it may be like Mouse is saying so try that. Use silicone dielectric grease on those connectors while you are at it. Somethin's loose somewhere!

[john grinsel]

How about burnt valve?

[scootermaven]

How about burnt valve?

Wouldn't it be hard to start, want to stall and run rough throughout?  This scooter runs good till you get right around 30 mph through around 45 mph and at about 4,500-5,000 rpm.  Before and above those numbers it doesn't hesitate.  If you get on the throttle as the hesitation begins, you can power through it.  If I'm in a 25-45 mph speed zone, where it doesn't require much throttle, it's really noticeable.   

[Stig / Major Tom]

A very few Like200i models developed a faulty Throttle Position Sensor  (TPS), only cured by installing a new throttle body. No other parts or systems were found at fault....and new parts or servicing had no affect on the stumble.
Symptoms were: easy starting, good idle, full throttle runs no problem - but very often a bad stumbling when trying for a steady cruise at moderate speeds.

Stig

[mousejunks]

What about a Throttle Position Sensor reset?

1. Put the side stand up and engine stopswitch is at "RUN".
2. Turn the key to the OFF position.
3. Fully open the throttle.
4. Turn the key to the ON position.
5. Release the throttle after waiting for 8 seconds.
6. Turn the key to the OFF position.
7. Turn the key to the ON position.
8. TPS and ISC have been reset successfully.

[Stig / Major Tom]

Please remind me if I'm mistaken - but, sadly, I  have no recollection of this reset procedure ever fixing an engine problem posted here. And it has been tried by many.
Easily done, so worth a try.
As I said, "nothing" solved the TPS fault on the LIKE200I'S - until the throttle body, or ECU, was replaced....new or used.
Stig

[CROSSBOLT]

Could this happen with no code?

[CROSSBOLT]

I re-read everything! We now know what it is not: no codes = not TPS or any EFI component misbehaving. Not stuck vent valve. Not overfill of engine oil. Not puke tube.
Mouse has a good recommendation on removing seat and tub to check LOOSE stuff on/around engine and induction.
I am now encouraging checking both power and ground points for loose connectors and loose ground points. Start at battery and chase + to fuse block. Chase - to every ground point.

[CROSSBOLT]

Any news?