2007 M8 wont rev

hey guys my lil bros sled wont rev past 68-7200 he said if he holds it there long enough it will eventually clean out and go but takes a really really long time. sled has slp pipe and can combo, 40/36 helix. primary has gold spring (dont recall the weights)
things we have done, checked and replaced spark plugs, new fuel. are the power valves out of adjustment? they have never been adjusted it has been ridden about 3 times this year with no issues.
no codes have come up either
we are wanting to ride tomorrow but this started happening. any help is appreciated.

cable is broken, can we tie them open and be able to ride? will it affect anything? if so how do you tie them open.
Thank you