Hi everyone. Im pretty stumped on this one. I purchased a tao110 in really clean condition. Had sat for a few years indoors, but no rust or heavy visable wear . Was not getting fuel or spark , so i decided to put a complete new harness and carb.
got it to fire up but it seemed it was running really lean
( popping from carb and a very light brown plug.) I adjusted the needle to every position, idle screw and a/f screw with almost no change. Thought it was weird so I swapped a slightly bigger carb. Now the bike would start and idle great but would BOG out completely when applying anything over half throttle. Seemed like a clogged jet or way to rich maybe? So i started adjusting the carb and got it to only bog down if I hammered the throttle off the line. If I eased into it it would be fine. Took the carb apart. Thourouly cleaned and checked everything. Same problem. I thought maybe the issue was on the engine side so I replaced all the head gaskets, intake seals/ gaskets. Adjusted the valves to 003" in and 004" ex.
flipped the head over and poured gas onto the valves while seated to see if the seats were bad.But they held. Had 120 psi in the piston so it had compression but without a leakdown tester i couldn't tell forsure if I was loosing compression. So I swapped a big bore piston and lower head. ... I could tell it had more power and wanted to go but it had the same bogging problem. Tried adjusting the pz20 carb on the big bore with no luck. Same issue. Swapped the pz19 carb back and I got the over lean condition again.. Tried a used carb that I know was working fine and still the same bogging... so I went another step and put the upper head off a pitbike that was running great... SAME BOGGING PROBLEM. No matter what I change or adjust I can't get the quad to run right. I have never had this much difficulty getting one to run.



so now I'm thinking even though I've put a new complete head/ 3 different carbs/ new Wiring harness. Swapped coils/ plugs/ CDI and stator.. I have no clue what's causing this issue. Could the harness be faulty or a bad ground cause this un tunable problem??? Any guidance appreciated. I'm sure I've missed some other things I've tried to get it to run right.

 

do you have the air filter on while doing all this adjusting... Sounds like it may have a air leak someware or you just have not found the sweet spot for the carb.. I know i have spent hours adjusting the AF screw, idle. and needle.. Also have you checked your floats and make sure they are adjusted properly. Did you clean out the fuel tank and lines? It may have gummed up enough to have slowed down the flow so it cannot keep up with the demand above idle

 

Exhaust plugged? Had an Eiger "trade in" that stood outside for a couple of years awaiting an engine rebuild. After rebuild it wouldn't rev, tried everything, then someone stood behind it while I was running the engine said "there are no exhaust gasses coming out" Couldn't un-plug it, and had to fit a replacement silencer.

 

so I should have mentioned. I tried both with and without filter on all setups. Also I replaced the tank and lines. I think merrman is right about it being the exhaust. I don't think it's plugged completely but something is wrong with it. I'm wondering how much the exhaust gasket would have an effect on this.

 

i think you are right again sir! Upon closer inspection it's not the carb popping but right at the exhaust port. I can feel air blasting out right around the studs. I'm guessing and hoping the lack of exhaust gasket is causing this problem

 

It isn't the lack of gasket, that may be the only place the gasses can escape, if separate, take the silencer (muffler) off and try it without one.