2010 crf450r jumping outta gear from 5th to 4th all other gears work fine

If you mean the engine just revs and there is no drive, maybe it has a gear selector issue. The 5th gear is like an overdrive.
I would take it to a Yamaha repair shop for advice.

Oh Dude, this isn't an easy fix. It sounds like your shift pawls could be bent, it also could be that the shift shaft that the pawls slide on is bent, worst case, there is some transmission gear engagement teeth that are damaged.

you need to either have a new trasmission put in or a new 5th gear new 5th is usually a little cheaper

If you just had the bike serviced, take it back to the tech that did the work. If you did the work your self, check the gear oil level on level ground with the bike in the vertical position (riding position). It sounds like the oil is low and this can cause the gears to not shift properly. I hope this helps.

Either the selector pawls are worn or the selector is out of adjustment. I would tell the sales guys that the bike is (however old it is) and if the gear box fails it will be due to the poor setting up of the machine, not the rider.
Has it always been like that? It only has to go between gears when you hit the power band and you will leave an awful lot of metal on the road!
Ride safe and a Happy New Year

Hi
This does sound like a gearbox problem, either where the cogs lock together (the dogs go into recesses) or the shift forks themselves
The dogs do wear after high mileage which can make them slip out of gear
Ive never heard of a gearbox smoothing out over such low mileage, but I suppose it is just possible
You could get the gearbox 'blueprinted' (i.e. to manufacturers exact specifications) but this will cost a bomb !
Your best bet is to complain again & at least get a ride on another rocket3, or get it sorted under warranty

Ride safe
Bike-Doc
Please mark this as very helpful (if it has been!!)

More than likely the shifter pawl has broken. Breaking in 5th gear is kind of unusual however, they usually break between first and second.

You'll have to remove the outer primary cover to look at the shifter pawl. It's partially covered by the clutch assembly.

Im not sure how you ride your bike but if you "beat on it shifting without cluch sometimes the fork in the transmission gets bent...this is the only reason that would cause hard shifting besides wrong gear lube

This behavior is the symptom that your clutch plates are getting worn out. Since power is transmitted from the cam shaft to the front sprocket (smaller dia) is better at lower gears but once the rpm increases the clutch plates do not catch up with the cams rotation, hence slipping at higher gears & in between 4th & 5th gears the pulling power of the engine seems to go to neutral before engaging again. Check your clutch plates as well as the sprocket-chain- rear sprocket for wearing out of the gear teeth & replace if required. You will get back full power & acceleration as when the bike was new.............sodeep

low engine oil will cause this hope it helps