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Tao Tao ATA125-A Stalling Out

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Tao Tao ATA125-A Stalling Out

noku0ut noku0ut
New User | Posts: 2 | Joined: 02/12
Posted: 02/05/12
01:17 PM

I bought this Chinese manufactured four-wheeler for our kids for Christmas and everything was working/running fine until one time when my son was riding it, it stalled out... for no apparent reason. Since then I have checked the spark plug, oil fill, fuel, battery charged and I have had no luck keeping it started when it is idle. When I start it up I have to give it gas to keep it running. When I push the thumb throttle all the way down it bogs down and when I let off of the gas (even slowly) it stalls out. Any ideas on what the problem could be? I'm thinking it may be the carburetor or something with the fuel line? But, I'm just learning about all of these things as I encounter one problem after another.  

thejunkman thejunkman
User | Posts: 101 | Joined: 01/12
Posted: 02/06/12
07:26 AM

This is fairly common on these types of machines.  Your problem is more than likely from improper setup out of the crate.  Mose likely cause is the fuel system is contaminated with debris from when it was manufactured.  Plastic casting flash or swarf could have been left in the tank from the injection molding process.  Remove the tank, fuel shut off, fuel line, and carburetor and throughly clean it.

Next possiblity is since the engine is breaking in the jetting requirments are changing so the carburetor needs some fine tuning.  The symtoms you describe is of a lean condition in the jetting which can be caused by a partially blocked fuel system or improper jetting.  Try the first remedy first.  If you are unfamiliar with carburetors or the fuel shut off valved watch these videos first.

Fuel Shut off dissasembly

Carburetor diagnosis

The Junk Man's Adventures show, For more how to videos  
Check out my webseries

noku0ut noku0ut
New User | Posts: 2 | Joined: 02/12
Posted: 02/06/12
02:32 PM

I am not familiar with carburetor cleaning and such, but I am learning a LOT about functions I had no idea about since I've bought this thing! I'm going to take a look at those videos... thanks for the reply and advice!  

thejunkman thejunkman
User | Posts: 101 | Joined: 01/12
Posted: 02/06/12
03:21 PM

No problem!  This is why I don't like about the Chinese stuff, it is usually the people that don't have previous mechanical or automotive knowledge that buy these things.  Its not that all of them are bad products it is the fact that they REQUIRE some setup and pre ride checks as well as a break in period.  All this is part of what you get from buying from a brick and mortar dealer.  IMO these things should never be bought used unless you know what your doing.  Don't forget to Like my facebook page  The Junk Man's Adventures and How to videos  
Check out my webseries

jessieherrera jessieherrera
User | Posts: 51 | Joined: 02/12
Posted: 02/12/12
03:34 AM

 It sounds like dirt got into your carb. You will need to take the carb bowl off and blow out all the passeges with an air hose. You may also have a vacuum leak. Check this by when it's running and up to tempreture by spraying starter fluid or hairspreay between the carburetor and head. If the RPM changes then that's your problem. This should fix the problem. If this doesn't fix the problem then repost and I will reply. I've included the following technical information:
Carb jetting:

 First, always run the carb dry when you are finished riding by shutting off the gas at the petcock and let it idle until it stops running. This is the best practice for any small or industrial engine. You may have a Mikuni. Even if you don't many carbs are similar in design and parts. Mikuni carbs are very easy to work with. Make sure that you have no vacuum leaks whatsoever.
Usually, the bigger the carb, the smaller the jets.
With today's gas it is almost impossible to read a spark plug. It used to be that if they were a soft white to a medium tan the mixture was correct. Today, you may want to try this to get the right mixture.
Adjusting you carb/mixture/jetting:
1. The idle air screw always starts at 1 1/2 turns from closed. Let the engine warm up and open or close an 1/8 of a turn at a time. Give it about 5 seconds to settle. Continue until the engine reaches its highest RPM/speed. This is called your best lean idle.
2. The cutaway on the slide regulates your mixture just off idle. The different cutaways enrich or lean the mixture.
3. The slow speed jet regulates the mixture until the needle in the slide takes over. This is initially about 850-1000RPM. Increase the jet size one at a time where you get the highest RPM at that slide or throttle position, not RPM as this will change with jet size. You should feel more power at that throttle position. Your needle on your slide should not be active or at the taper.
4. The needle in the slide regulates the mixture to wide open throttle. The needle has a taper to it which regulates the fuel amount from the main jet. It also has a few notches that will raise or lower the needle. Raising position enriches. You will feel more power at that throttle position.
5. The main jet regulates the mixture at "wide open" throttle. Read below to adjust.
I have found that the best way to jet your engine is by what's called "seat of the pants performance".
Adjust the jet size by enriching the jet until you get the highest RPM/speed at that specific RPM/throttle position. An example would be the slow speed jet at let’s say, 850-1000 RPM though this will change with the richer jet so actually it's better to go by slide position.
The high speed jet you do by accelerating through the gears until you reach top end. Keep increasing the size one size at a time until you get the maximum speed and feel of power. Once that is reached go down one jet size.
With different pipes and types of driving as well as types of intakes jetting will change. Altitude is also a factor. An example of intakes would be velocity stacks or air cleaner inside configurations. Different lengths of these passages affect you RPM and acceleration. High performance demand will always require richer mixtures as moderate driving will perform better at leaner mixtures.

 Your timing may be either too far advanced or not advancing at all. Check with a timing light. Your mechanical advance (if so equipped) may be stuck or broken or your flywheel may have shifted though neither of these are likely, but possible.
 On your flywheel there should be several marks, one should be TDC or your cam alignment mark. This one puts your piston at TDC and is used for cam reference.
 The next should be your "static" or initial timing mark. This one is used to set you basic timing. Timing can vary depending on your vehicle. They usually range from 2 degrees ATDC to 14 degrees BTDC.
 The last one should be your total advance mark. This one is usually around 35 degrees and can be checked with a timing light above 1500 RPM. Your total advance is where your top end power is created. You can advance it until your best power is achieved. If advanced too far it can cause pinging "predetonation" which can destroy your engine.
Good luck.