Author Topic: Agility 125 won't go over 35mph SOMETIMES (Read 3528 times)

donatello · « **on:** April 02, 2015, 03:21:45 AM »

I have a 2009 Kymco Agility 125 that has performed well for about a year now. I drive the scooter about 15 miles per day and am able to reach over 65mph typically on an open road. Every few days or so, when I start the engine the acceleration is really slow and I can't go over 35mph. The weird part is when I shut off the engine and start it up again a few hours later, the performance will most of the time go back to normal.
I first removed the cvt cover and replaced the belt since it has been a couple of thousand miles since I last did that - also changed the variator rollers and clutch since they have never been changed. The problem still persisted so I put seafoam in the gas tank to help unclog the fuel lines and carb. I plan to remove the carb tonight and drown it in carb cleaner hoping that will solve the problem. Im hoping I won't have to replace fuel lines or dig into this problem much further. My next guess would be to replace the fuel filter but I am uncertain of what benefits that may provide. Anyone have this problem before or have any wisdom to share on this issue? Thanks!

tortoise · « **Reply #1 on:** April 02, 2015, 03:40:14 AM »

Quote from: donatello on April 02, 2015, 03:21:45 AM

plan to remove the carb

Also remove rubber intake manifold and smear silicone grease on the carb and head join surfaces to deter vacuum leaks. If carb slide assembly is not rising properly, the diaphragm may be deficient.

donatello · « **Reply #2 on:** April 06, 2015, 09:44:12 AM »

Thanks for the advice tortoise. I cleaned the carb and fuel filter and it did the same thing again today. Twice actually both times while I was suddenly turning left at a stop light.

Anyway, since the diaphragm is cheap I purchased a new one. Took the carb apart and noticed the upper rubber part had a tear in the outer ring portion. I will replace diaphragm and smear grease on the join surfaces and let you know if that fixes the problem.

donatello · « **Reply #3 on:** April 07, 2015, 10:46:22 PM »

Another question. I haven't received the new diaphragm in the mail yet but still ride the scooter around.

I am wondering what the standard number (or range) of turns for the fuel mix screw should be after fully tightening the screw? on a 4 stroke motor

If there is no standard then I will play with the mixture once I receive the replacement diaphragm. It seems a bit rich right now but I will see if the new diaphragm changes that.

Jim Moore · « **Reply #4 on:** April 08, 2015, 10:30:55 AM »

Quote from: donatello on April 06, 2015, 09:44:12 AM

Anyway, since the diaphragm is cheap I purchased a new one. Took the carb apart and noticed the upper rubber part had a tear in the outer ring portion. I will replace diaphragm and smear grease on the join surfaces and let you know if that fixes the problem.

I'll bet that's it. The torn diaphragm is not creating enough vacuum to pull the needle out of the main jet. No idea why it's intermittent though.

donatello · « **Reply #5 on:** April 13, 2015, 11:33:41 PM »

I went ahead and replaced the diaphragm. Immediately performance went back to normal. The speed was there and the engine ran smooth, until yesterday. The engine had a really hard time starting up - took about 20 seconds each time (4x a day).

Today as I was driving the scooter and had stopped at a stoplight i noticed the engine idling really low. As i pulled the throttle to go, I went no faster than 25mph. I have no tachometer so I am not sure how many rpm's the engine was getting, but it felt like the engine wasn't even revving up. Im no expert on engine noise but it sounded as if the engine wasn't getting enough fuel. Now every time I twist the throttle at a stop, the engine will die or almost die. HELP PLEASE!

donatello · « **Reply #6 on:** April 14, 2015, 06:11:49 AM »

After much research, I figured I would change the fuel lines and filter and clean the fuel petcock.

I havent gotten around to clean the petcock or replacing any fuel lines or filter yet. Although I opened up the carb and readjusted the diaphragm. Voila! That fixed the problem and immediately performance went back to normal.

I now am afraid that the vacuum slide or diaphragm (whichever term is preferred here?) will continue to get stuck in the carb. Does anyone has any solutions to prevent the diaphragm from sticking? I've heard of sanding down the varnish in the carb bore but I don't see any and the carb seems to be smooth, slick, and shiny. I don't wanna mess with anything before I got some advice first. Any suggestions??? Please & Thanks ahead of time!

donatello · « **Reply #7 on:** April 23, 2015, 02:23:59 AM »

Hey guys, I'm back. So the problem continues to happen, however, I discovered that the problem is simple - the rubber diaphragm continues to get stuck in the carb and fails to lift as I pull the throttle. I plan to replace all fuel and vacuum lines in the case there is dirt or gunk in any of the lines.

Does anyone know any other potential problems that may affect the vacuum in the carb?

Are there any solutions to preventing the rubber diaphragm from getting stuck?
(i.e. sanding down the bore of the carb to remove varnish (assuming theres any), putting a very slight amount of grease on the vacuum slide to prevent locking, etc.) I haven't tried anything yet but am wondering if anyone has experimented with this problem?

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