I have a baja 90cc atv that wont run smooth at much more than an idle speed. It starts and idles just fine. If you give it throttle it quickly starts to pick up but quickly starts running rough and the engine will not wind on up like its supposed to do.
I have removed and cleaned the carb with no noticable difference. How do I identify my carb? From pics online it appears to be a mikuni pz19 with shutoff. But just inside the intake throat there is a #16 which makes me think its a PZ16. Problem is in looking at rebuild kits for both it is neither because the 16 had a completely different float but the 19 kits have a different shape gasket for the bowl. ?????
After I determine what carb I have I need to know how to adjust the float. And does anyone know where the little spring goes that is in the float chamber. I cant seem to find anywhere is would go other than against the float lever but that would hold the needle closed all the time.
I know I have asked several different questions here but lastly what else could it be? This thing is driving me nuts and I hate to take it somewhere and pay someone to fix something simply I have missed.

 

no one?

 

running rough could be these:
too rich-check spark plug electrode color
too lean-check spark plug electrode color
jets partially plugged but not enough to bog the quad way down-pull jets and clean them thoroughly.
rev limiter-last resort after previous 3 have been exhausted.

check for vacuum leaks around intake boot by spraying carb cleaner or ether/starting fluid(in the area of the intake boot) to see if it revs up while spraying and the quad is running.
is there not a hole for the float return spring to hook into around the tab area?
plenty of videos on youtube about cleaning/adjusting carbs and floats.
it'll be a couple of days before i can get to my chinese carbs to see exactly where they anchor on the tab area. if you can, take a few pics and post them and we can go from there.

 

I have cleaned the carb thoroughly. (I think anyway) pulled all the parts, soaked jets then blasted with carb cleaner then with compressed air. Reassemble everything, no real change. Pulled plug and the entire thing was black. Not really oily black looked more like dry carbon. Gave it a good wire brushing, no change. I have unplugged the rev limiter and that changes nothing either.

 

black spark plug is way too rich. adjust the carb and let's go from there. you could see daylight through all of the orifices in the jets and down the centers of them, right?

 

yes I could see light and I blew cleaner and compressed air through every hole I could find. I have adjusted it before, all the way from closed to backed out so far I was afraid the screw was gonna blow out the hole. It still runs like crap. I can hold the throttle open while I do run the screw in and out and it hardly makes any noticable difference. Thats why Im so friggin confused with this thing. ONly screw I have ever turned on this thing that really made a difference was the idle screw. And seems about every month or so I have to readjust that as well. I have found a new carb online for about $20. Think I should just invest in that?

 

Have you done a compression test?

 

No I haven't. What should it be and I will check it.

 

<90 psig

 

With throttle closed the compression if 85 and WOT its 160. I think I am definately chasing a rich condition. When I pulled the plug to check compression I noticed it was real black again. Cleaned and reinstalled it. Set carb 1 1/8 turns out per service manual. Started it up and its a little better but far from right. It ran maybe all of three min. Pulled the plug and its black and wet. I thinking either the needle is leaking or the float is off and its just dumping fuel all the time. Does anyone have a diagram of where and how the little spring goes on the float lever. I believe that may be my issue.