You might think is too simple and crazy but i would flush out all the gas and put some fresh gas in
I think you have an intermittent coil or further down the line spark issue....
First new spark plug--- that has happened so many times -- hidden by the eye or deceived by "but it is a new plug why question it"

I would double check the connectors to the coil under the front plastic "hood" and make sure the connectors (metal) and not plastic and metal is contacting the coil terminals and then use side cutters to crimp the metal further on to the coil connectors -- ensuring no room for vibration issues

Perhaps its like someone mentioned a faulty "intermittent" cdi further down the line

 

Sorry it took me so long to get back to you guys......had some racing of my own to do......of course got rained out........typical Michigan weather.

Dejardins.................I'll get some pics up tomorrow. Thanks for all the help and directions.

Jaster.............no one failed but me, usually I am pretty good at this stuff......built, rebuilt or played with this stuff most of my life, but everyone has their "Eleanor" LOL. My drag car is WAY easier to figure out when it hiccups but this damn thing is killing me...LOL

Lynn, Yes I have done some test after she runs. After I got the spacer / manifold fixed...(I fixed the plastic spacer and also ordered a new one, milled the manifold flat on both ends and also increased the o-ring size on both the carb and spacer) No more vacuum issues. After the ATV starts (again max 30 seconds) The plug is wet with fuel and you can smell fuel. On a whim I pulled the new carb apart, cleaned everthing, made sure the jets were free and clear. Float is working properly and not stuck. I did tighten the leads to the coil and low and behold the machines fired and ran the longest it ever did, got excited and as I was about to let the thing idle and put the seat on, it died and never started again, checked the plug for spark immediately after and the spark was very small and weak, the plug was wet though (better than ever before). So to me this eliminated the fuel issue.

One thing that does concern me..........I have tried to start this thing on Ether /Starting fluid and it has never fired once....very confusing. Maybe I have been chasing the wrong issue. I strongly believe I have the fuel issue solved, but not my problem. Machine will only run for a very short time (30 or so seconds, when I do get it started, then it will not start again, until I let it sit, diag something and then it will attempt to start but never fire.

PS I never got to check the timing since I never have had it running long enough to do so. I currently do not have an adapter for the small thread size in the head to test for compression, but the simple finger test it will blow your hand off the hole. and also putting it in gear and roller the ATV forward you can feel the compression stroke when pushing.

Thanks guys for all the ideas, we are close just missing one key component.

Jim

 

Thanks Smith!
I did has you suggested, drained all the fuel, blew out the lines and tank and added new 93 octane........no change.
I have also tried 2 NGK plugs (Bought two when I first got the ATV). So chances are not the plugs.
I did crimp the leads and it did start and run after, but still died out after 30 seconds or so.

I am thinking the same thing about the coil or CDI, It is still under warranty and they will send me the parts, in the meantime I can use some of Lynns test methods I found elsewhere on this site......

Thanks again !

 

It's good that you are looking at this in a fresh light.

I would do the ignition system tests while the engine won't start - and the spark is weak. If it is your ignition system that is the problem then hopefully these tests will turn something up.

 

Couple things:

1. Make sure you are well grounded. If you have a bad ground that could cause some intermittent electrical problems.

2. Adjust the valves. I think intake/exhaust valve clearance should be between .005 and .009. Need to get the motor at TDC, then check your clearances with a feeler. Don't trust that they are set properly - this is a chinese product afterall.

Good luck!

 

First off I want to say thank you to everyone who posted or sent me a message concerning my little Tao Tao 125 A ATV.

After exhausting every single possibility in my knowledge base, I took the ATV to a somewhat local 1 hour and 15 minutes away Bike / ATV shop "Howell Motorsports" (great guys to deal with). They did all the usual diagnostic evaluations, same as me and then started in on the electrical system. Everything "Checked" out okay and they were a little stumped (of course mine is the bastard that no one can figure out). Well on a whim they had an identical unit like mine and took off the Parental controls, alarm control module and replaced it with the one from the showroom, and BOOM.........the thing started right up and drove it all over the parking lot. Come to find out the box had some type of short that was intermittent and would cause all kinds of issues not allowing the thing to run or start. 3 hours of diag time and a $40 part, and after 8 weeks, i was finally able to ride the damn thing and my son comes home tomorrow, so he will be able to ride it !!!

PS..Please avoid the online company known as "Budget ATV's" nice help in the beginning, turned real sour towards the end and now will not answer emails or phone calls. BBB in Texas has 4 open cases against them, but cannot be closed due to no physical address for the company. Imagine that, what a surprise.

Thanks again !
Jim G.

 

Thank you for replying back. This is a strange problem, but it does make a little sense. If we had unplugged the remote it would have been out of the picture, and your quad would have run. I will add that test (unplugging the remote module) to the generic 5 pin CDI "no spark" trouble shooting procedure.

You do have the 5 pin CDI right?

When you post back stuff like this the knowledge base grows. This will help a lot of people down the line... .

 

Congrats on figuring out your problem!

 

Yes Lynn it is the 5 pin CDI box. Part number are the same for the 110cc and the 125cc.

Thanks Again !
Jim

 

My son 4 wheeler have been sitting for 3 months because its wouldn't start and i haven't had the time to get around to it. So i try to start the other day and it does but when i hit the gas it cuts back. It wont go more than half way. Please help