yamaha yz250f

So I’ve had this bike 6 years and it had a full rebuild when I got it and I verified but this past couple years it has sat a while because the water pump failed and I was broke and never fixed it but eventually I did and broke a side case cover bolt right next to where one was already broke off...

Hell i desperately need help, I am going riding in 2 days and i have this terrible noise coming from my YZ250F especially when i rev it (sound like a high pitched whining noise, not like the good old deep rumble of a 250f) it sounds like its from the timing chain area. I have checked the chain...