make sure carb is opening up if uncertain remove and put gas directly into cylinder caution not to much if still doesn't work valve may be stuck or bent. If blows fuel back out at you intake valve stuck open if when you hold dollar bill at exhaust it sucks in exhaust valve stuck if unit is timed correctly hope this helps .

 

I agree with you and suspect valves as well.
Why were the valves adjusted in the 1st place if the machine was running perfectly?(I get this from the OP 1st post). Usually this happens if valves are not adjusted correctly. (Yesterday I repaired an engine which had exactly the same problem because the owner had adjusted the valves thinking he would get more power with better compression.)

 

I have the same bike I’m having problems with if anyone would have any ideas would be great, first of all the dash is saying it’s in reverse when in neutral, r light on dash and n light is off, do these have a neutral switch? Or is it those 2 sensors in the cvt. Could that be the problem? Or am I looking in the wrong area, it won’t turn over by the start switch due to this, but will turn over if I put power to the starter, also it back fires through the carb and makes a big clunk, but then sometimes it’ll spit a flame out the exhaust, timing is 100% right, it has a new cdi, coil, spark plug, just ordered a starter clutch to try eliminate the clunk when turning over, it’s definitly got spark and compression, carb is brand new aswell