50cc idles but won't Rev

[HitShane]

Hi,


So I have a 2013 50cc TaoTao ATM50-A1. I have put 1200 miles on it since I bought it new. I use premium fuel and have followed the maintenance schedule. I have a new carb installed, vacuum lines, fuel lines, fuel petcock, fuel filter, and sparkplug. It has ran great since I got the new carb a few months ago.


While I was driving home last week it felt like it was losing power and slowed to about 20MPH, but made it home. I thought it was the rear tire as it has a leak and I have been looking up replacements for it.


I started my scooter yesterday to go to the store and it started just fine. I let it warm up till the RPM's dropped into a nice idle and went to give it gas. No power at all and it bogs down like its choking. If I let off the throttle quick enough it catches back into idle otherwise it dies. After doing this a few times it started not staying at idle and was bogging out no matter what.


I pulled the carb and took it apart. Every part inside of it looks brand new and shiny. I used compressed air and blew through every orifice and the jets. I can feel air coming through the other side of every thing I blew it through. The diaphragm looks nice and new and I can't see any holes in it. The needle was not stuck or the floats.


I reinstalled the carb today and while starting it I saw fuel come through the lines and into the carb. After a few tries it started right up, but idled bad. I opened up the gas cap thinking maybe it was vapor locked and it starts but still wont rev without choking out. I opened the air box and still the same thing. I blocked the air intake with a T shirt and it didn't get better. I felt the exhaust and the pressure feels nice and strong coming out at idle so it must not be blocked. I normally have the fuel mix screw between 2 and 2 1/2 turns out. I had to turn out the screw about 6 turns to get it to idle correctly. Still bogs out the same. I swapped out my expensive spark plug for a basic NGK it came with just for the hell of it and it didn't change anything.


Just touching the throttle bogs it instantly. Turning the fuel screw out makes the idle higher and turning it in kills it. It is not where I normally keep it though and it is turned out about 3 times more than normal operation to keep it idling nice and strong. If I turn it out anymore the screw is going to come out.


Can someone tell me where to diagnose next please. I don't see where it could be losing vacuum and it is getting fuel. The intake and exhaust aren't blocked. The carb isn't clogged. The enricher is still functioning. The engine sounds fine now at idle with the current carb screw position. The plug I pulled looked fine. It has proper oil and there are no fluid leaks or buildup anywhere. Could the PAIR system be clogged up? Could it be exhaust valve? Could it be the CDI? My next step is draining the fuel and replacing the CDI and coil. Should I buy a compression tester? Replace the carb first?


Can someone jump in and share some knowledge please


-Shane

Edit:

OK,

So I had a window today of no rain and went to work. I aligned the timing mark and double checked the cams placement. The engine rolled into the sweet spot to work on the valves.

I checked them before I loosened up the nut and both in and out were .005". The shop I got it from said they adjusted the valves to get the best performance out of it when I bought it, so I'm guessing that's where they put it at. The ripped rubber gasket reinforced this conclusion.

I set both valves at .003" and tightened them up carefully. I rotated the engine a few times from the air fan and rechecked them. Perfect! I reinstalled the valve cover, being careful not to strip the bolts! So far so good...

I put the carb fuel mix screw where it should be and it wouldn't start. I turned out the screw until it was about to fall out and was able to get it to slow idle. Turning the throttle even a hair, causes it to bog out. It actually was idling better before I made the valves tighter. I might go out to .004" after I get it running, but I still have to do that first.

What is the next thing I should do? Should I order a carb? Can someone send me a link to a carb that is good and not Expensive as hell! I have the one with the black plastic diaphragm cover on it now.

-Shane

[dwint51]

mine was doing that with the throttle and my pilot jet was clogged

[Madathlon]

Does your Carburetor have an Carburetor Diaphragm if so here a tip. I had the same issue with mine.

Mechanics Note: If the engine is sluggish or won't allow you to run her up much past half on the throttle, and you are having difficulty getting her to full speed, look in the carburetor with the intake boot off, and see if the diaphragm is going all the way up. If it fails to do so, it is torn or leaking and you have found your problem.

http://www.scooterpartsexpress.com/s...-tng-vento-vip