I have YFM350ER I replace the top end once and it ran amazing but I forgot to tighten the sprocket bolt to 45ft/lb and as I was riding it shear the camshaft I asked the company to send me a new one and I put the new one in and now it not wanting to start I know it’s the a fuel issues. It backfire and after cranking for a bit I get carb fouled plug I pulled the carb out and changed the height of the main jet needle so it was leaner and put it all back together and make sure everything was tight it would run if I played with the throttle with a flat head screw driver in where the cable hooks on but if I went higher then a 3/4 inch to a inch it would would like piston slap but a soon and I stop it would sound fine I got it to start for a second but it didn’t set the idle screw so it would drop down and die I went back reinstalled after cleaning it and priming the pump but I can’t get anything out of other then the occasional backfire that rattles my garage