shifting problems, help!
 

I have a KONA lava dome XC bike with 7sp, I recently replaced the chain for a sram 7/8spd, now the shifting is out, it jumps under load in most gears, its not trying to change gear but the chain skips then reengages, tried all kinds of rear mech adjustment but they made no difference, what causes chain skipping

Your cassette is worn out... you should almost always replace the cassette when you replace a chain because they wear together.