2010 SunL 125CC. It Idles but does not throttle up. I have replaced the Carb with a NEW Carb. I thought it was the throttle needle and sleeve in the beginning but it came with the new carb and still performing as described. It's getting spark and fuel. I have replaced the fuel filter between the tank and carb.

I have ran out of options of what the problem could be. Anyone have some ideas?

Michael

 

where the throttle cable enters the carb, is it on top or the side? what i'm getting at is this: if through the top, is it a slide on the inside? have you pulled the carb and looked inside while stroking the throttle? does anything move inside the carb? surely it ain't as easy as the throttle cable already being broke....pull the carb, leave the cable connected and look inside as you stroke the throttle. you may need to adjust the throttle cable at the turnbuckle which may be located about 12" from the thumb throttle. 2 jamb nuts and a stretcher. i know you said a new carb, but let's rule out this other stuff as i see you didn't mention any other checks you've completed.

 

Throttle cable enters the carb from the top. There is a slide/sleeve with the throttle needle inside it which moves fluently when pushing on the throttle. I wish it was that simple with the cable being broke, Unfortunately that's not it. Everything inside the carb is moving when thumb throttle is being pressed but runs in an idle state. I do have to keep the thumb throttle pressed about a finger widths in order for it to sustain an idle, but unresponsive pressing the thumb throttle to the max.
Here's the carb I have: 50cc 70cc 90cc 110cc 125cc 135 ATV Quad Go Kart Carburetor Carb taotao Sunl PZ19 | eBay

The turnbuckle is closed meaning the stretcher is flush against the jamb nut.

 

take the float bowl off and inspect the jets. make sure they're clean. if it won't idle without you feathering it a little, the idle screw is out of adjustment OR it's fine and the jet is partially plugged. but you would think with brand new she ought to take off!

 

Yes you would think so. I did what you explained to the old carb and produced the same results. Maybe its not getting enough fuel flow thru the HIGH end of the jet. I'll have to take the tank off and see if there's anything slowing down the gravity feed of the fuel. I'm not sure if that matters but worth a shot. It's really frustrating because my son has ridden this thing to the ground! The exhaust flange broke and was repaired about a month later. I hope a valve wasn't burnt up during the course of him riding it that way.

 

make sure the exhaust isn't plugged. If you pull the exhaust off at the head and it revs up then you have a plugged exhaust.

 

Seeins the carb seems fine, I would look into the valve adjustment/valves. As you stated, you know there is a good chance of wear/trouble..

 

Dumb question maybe, but have you tried a new spark plug? If it fires and idles but does the same thing with a new carb, it may not be fuel related but ignition related. As mentioned the valves could also be out of wack. If your intake isn't opening enough you may be starving it for fuel at high revs. When you mentioned that the exhaust flange broke, it crossed my mind that maybe something else broke in the exhaust causing a partially plugged exhaust. If you try to rev the bike up does it just die right out or bog out. Try reving up, then shut it down and pull the plug.Is it wet with unburnt fuel or dry like no fuel is getting to the combustion chamber? Beg borrow or buy a decent spark tester. Check your spark for colour. Should be a sharp blue arc. Probably there are more things to try but I can't think of them just at the moment. Try these things one at a time and you may come up with an answer. Also try a compression test although if it fires and idles that may be not a problem.

 

I have pulled the plug, just to test spark. It has a blue white spark but didn't think to notice any moisture on the plug itself. A few friends of mine have mentioned something about the spark plug. I will test and advise, I should probably just spend a few bucks and get a new one.


I can keep it running with a fingers width push on the thumb throttle but anything pushed beyond that point that engine stays as is, does nothing. Very strange and off if you ask me.

 

Valves and/or compression...