So 5 days ago a friend picked up a 1999 400ex they let us test drive it and it wasn’t in the best condition but we ended up buying it for $1000. She said it was ticking because the valves needed adjusted so we took it to another guys house who works on atvs he tensioned the camchain and we rode it a couple times and it acted fine. That night we were gonna go on a little ride and probably 10 minutes in the kid driving it said he downshifted and heard a noise like a knock in the engine and it shut off. After that we couldnt get it started. So the next day it did the same thing run for a little then shut off and after that point when we tried starting it the starter motor would just spin. So the next day we worked on it a little cause it needed a little tlc anyway so I adjusted the valves and we pit a new spark plug in. Then we hooked it up to the back of another fourwheeler and roll started it ran fine but could still here some ticking it even died and he pressed the button and it fired right back up. when we got it to my house at that point we roll started it and it drove for a little and we had to turn it off to fix a bolt in the shock after that point. nothing was going right. When we would try to roll start it it would start but only stay running with the throttle wide open and it had to be moving from being pulled to stay on. So we cleaned the air filter and took the carb and sprayed some cleaner in it. tried it again same thing. So tonight we took the carb apart and cleaned everything including the jets. Once again will start when in motion from being pulled but won’t accelerate and wont stay running unless being pulled. sorry it was so long but we need help.