250-500cc WR360 Problem with shifting gears up

Hello everyone! ive searched alot of forums but they had some differences from mine and couldnt really find an answer. soo thats why i make this new thread.
Ive started to occur problem with shifting up on my WR 360 1999. with or without clutch it just doesnt wanna shift up at high rpms. when iam at low rpms it works. or ussualy when i go high rpm. let off the throttle and quickly shift up. Then it sometimes work.
but if i give it full throttle and try to shift its no chance. Ive read that it could be forks. but wouldnt that shift at all then?
- shifting down is no problem at all.
- changed oil (10w60) = no change
Thank you all!

Don't use full throttle to shift up.
Or let off slightly then ease it in to gear.

That's the wrong oil like I've said before 10w40 or thinner will be off benefit to getting up to working temperature faster.

Yep! i never use full throttle as its not neccasery and i always shift with clutch. was just testing out how will it react while this problem.

Okay i will try The 10W40 then and see .) thank you

my 99 360 is hard to shift sometimes
I change the oil and use a synthetic oil it seems fine
usually Maxima or BelRay

Alright thanks! The shifting isnt grinding or hard or anything. It just simply goes through without getting the gear up (I lift the shift lever and nothing happens, sometimes)

it seems like it does not pull all the way up to me

Yep. but at low rpms its no problem. i will open the left case and see

I've got a 6 speed out of a 360 in my 07 wr250. I was having a little trouble shifting and upon inspection the hook that grabs the pins on the selector had a groove? worn in it. I replaced it and cured the shift problem.

my 360 always shifts excellent, and i usually only use the clutch downshifting. i just let off to up shift. check under the clutch case to make sure everything is tight..
others are correct, try using a motorcycle engine oil around 30w or 40w..will work much better

Found it out! anyone with the same problem check this out. And big like and thanks to WVdag for tiping it out!: "the hook that grabs the pins on the selector had a groove?"
It was worn

Result. Now to find a replacement/repair.. probably weld it and file it back good.

Yes! thank u soo much for help! .)