2009 Agility 50 - Carburetor Issues

[JefeLoco]

I have a 2009 Kymco Agility 50 that is currently experiencing some suspected carburetor issues.  I have cleaned the carb jets as well as all passageways through the carburetor and the problem still exists.  The problem I am experiencing is that the engine will stumble and stall when running at about 1/4 throttle.  This could normally be adjusted with the idle mixture screw but the mixture screw on this carburetor has a tamper-proof screw installed (as opposed to the standard flat-blade screw).  I would imagine there is a special tool that will connect with this tamper-proof screw, but so far I have been unsuccessful in finding such a tool.

I have checked all vacuum lines and have no leaks anywhere on the engine.  I am very mechanically-inclined and am stumped on this one!  I'd greatly appreciate the assistance of some real Kymco experts

[Rianna]

Hi, Jefe. I'm new to scoots and don't know a whole lot, but I do have an Agility 50 manual. If your spark is good and you're sure there are no air leaks then these are the remaining things I can see in the manual that could cause problems.

CDI unit
Pulser coil
A.C. generator
Air cut-off valve

Don't know if that will be any help. Some other folks with more experience than me will likely come along with more info for ya. Good luck.

And welcome to the forum.

[JefeLoco]

Rianna,

Thank you for your reply.

I believe the ignition system is working properly on the bike.  The way the engine quits at a certain RPM range tells me that it's fuel-related. 

What is the air cut-off valve you mentioned?

[Rianna]

You will need to remove these two screws in the pic here to get to it, Jefe. I'll include what the manual says about inspecting it for ya.

AIR CUT-OFF VALVE

DISASSEMBLY
Remove the two screws attaching the
throttle cable set plate and the set plate.

Remove the two screws attaching the air
cut-off valve.

Remove the spring and vacuum diaphragm.

Check the vacuum diaphragm for cracks or
damage and check each passage for
clogging.


ASSEMBLY
Install the vacuum diaphragm onto the
carburetor.

Install the spring and air cut-off valve cover.

Install the throttle cable set plate and tighten
the two screws.

• Be sure to set the vacuum diaphragm
lip into the groove on the carburetor.

• When installing the air cut-off valve
cover, make sure that the vacuum
diaphragm is properly installed.

[JefeLoco]

Rianna,

Thank you for your post.  Is there anything listed in your manual regarding adjusting the idle mixture on the carburetor?  I've check all diaphragms on the carb and they look fine.  The scooter has about 400 km on the clock.  What boggles my mind is how the engine can idle and somewhat accelerate, which tells me that the idle jet is working fine and there are no air leaks, however, after it reaches a certain rpm range, it just quits.  If I open and close the throttle quickly, I can get the engine to run past the "problem rpm" range and reach full throttle speeds, but it takes some finesse.

I've installed a 55 micron fuel-filter thinking it would stop these carb problems, but it has not.

SO FRUSTRATED!

[blue]

hi jef for that mix scew you can get lose you can take a dremal tool or a small hack saw blade and cut a small line in it big enough to make a screw driver fit on it. I had to do that to the top of my carb because one of the screws wear broken. and also did you do any up grades to your scoot did you cut the cdi box or replace the boss or the jet. if not you might wana try a bigger jet which well help you out a great deal. and if you had the carb apart at one time make sure the float is put back in just right
or you well have that problem. sometimes it just might be something simple like the airfilter dirty or a gas line needs cleaned. try seam foam for that. good luck let us know what more we can do to help.

[Rianna]

These are the things I can see in the manual about the idle speed:


CARBURETOR IDLE SPEED
• The engine must be warm for accurate
idle speed inspection and adjustment.
Remove the inspection cover.
Warm up the engine before this operation.
Start the engine and connect a tachometer.
Turn the throttle stop screw to obtain the
specified idle speed.
Idle Speed: 1900 100rpm
When the engine misses or run erratic, adjust
the pilot screw.

Pilot screw opening
2±1/2

Remove the main jet, needle jet holder,
needle jet, slow jet and pilot screw.

• Be careful not to damage the fuel jets
and pilot screw.
• Before removing, turn the pilot screw
in and carefully count the number of
turns until it seats lightly and then
make a note of this.
• Do not force the pilot screw against its
seat to avoid seat damage.

Clean the removed fuel jets with detergent
oil and blow them open with compressed
air.
Blow compressed air through all passages
of the carburetor body.

And some more things I saw in the troubleshooting section:

Engine speed does not
increase sufficiently

Clogged air cleaner/air vent hole
Poor quality fuel (Restricted)
Clogged fuel tank cap breather hole
Clogged exhaust muffler
Faulty auto bystarter
Split carburetor vacuum piston
diaphragm
Faulty auto fuel valve

How are the valve clearances, Jefe? Is everything operating properly there?