the sound of a slippin tranny

[Kesh636]

i have a 06 636 and few weeks ago, i got a hole in the rad but heres the thing, before the hole appeared in the rad the bike sounded like the tranny was slippin when i just get on it and go while im riding, then the rad had got a hole. so i got the bike home thinkin that i just needed more oil. i swapped out the rad two days ago put more oil in it cause it was low.got the bike running and test driving it. now heres the kicker, the bike still doin the same thing, whinding out then picks up. bike shifts really good. now when i try ti just clutch it up for a small wheelie, bike whinds out the picks up strong. i was told that i could be the cable clutch is tight. not sure what it could be hoping its not pressure plates or needing a new tranny.

any suggestion or good advice would be apperciated