rancher 350 cutting out at half throttle

2005 Rancher 350 ,HMF ,bored out to the Max limit,carb jetted up . Ran great for about a month. Now starts cutting out at half throttle. Sounds like a rev limiter.
Also, it won’t hold back in any gear when you let off the throttle going down hill or any time. It just recently started doing this.

Any help would be greatly appreciated to the max!