Hello, I am trying to get my sisters atv up and running again but stumbling over some issues. This machine fires up and runs with choke only. If I attempt to add throttle it cuts right out. attempt to open choke- dies immediately. I have verified fuel supply to carburetor. have cleaned and inspected carburetor jets multiple times. still nothing. This machine already has a manual choke- and it seems to be working fine. As expected, when placing an obstruction behind the back of carb. i will run better (increasing vacuum in carb). Im getting frustrated with this and reaching out for help. Checked vacuum on line in intake boot. has 10in lbs at idle. when throttle applied there is no vacuum present and engine dies. What could be doing that? I know vacuum should drop some with throttle opening, but it seems as if the moment i touch throttle it completely loses it and dies. maybe valve timing? maybe I'm over analyzing this because I do this all day on cars for a living? maybe its simpler than i am making it? please help!! lol

 

if you have found no leaks in the intake piping, usually the instant bogging down of the quad is due to plugged jets/partially plugged jets. i know you said you cleaned them, but do it again. this is what i use: obviously carb cleaner, compressed air, AND to me the most important tool, is the oxy/acetylene torch tip cleaner pack. those little rods can get into the orifices of the jets.
your jet may not look exactly like this one, BUT, this is an example to show you. see the little orifices? rod those out until you see nothing but daylight and brass. keep it wet with carb cleaner while doing this and blow air through it and around it. it'll keep the muck at bay. don't forget to go down the throat axially also. do both jets. don't get discouraged or impatient. i did this the other day with a buddy's quad, 6 times i cleaned the jets, he didn't have a filter and we cleaned the tank, but didn't have hose material, the solids seem to come out of nowhere on us even after we flushed everything. as you'll see by the size of the orifices, it don't take much to plug them off. good luck. let us know and we'll help you some more. good starting point.

 

okay, so now a little more info comes along. while having the engine running, i sprayed aroung for intake/vacuum leaks with carb clean. I found that every time it got even close to the left side of the carb the idle would race. Of course i tried like crazy to pinpoint the air leak and was unsuccessful. So i got my evap smoke machine out... isolated the carb and found that where the choke cable mounts into the carb was leaking. new o-ring and re-smoke and it was great!! UNTIL I looked at the handlebars and found smoke coming from the other end of the choke cable (the choke lever on the handlebars). shouldn't happen, right?