RD highest gear wont shift up
 

the rd on my 7 gear bike hybrid is on the highest gear it doesnt want to shift up to the 2nd highest gear when i try to change the gear up 1 but it will just go halfway before it stops and stays.the cables are relativity clean and chain too.i have made sure to line up the highest gear with the rd and looks perfectly straight aliened so its not bent or anything.

Not the best description to really know what's going on. "it doesn't want to shift up to the 2nd highest gear when i try to change the gear up 1 but it will just go halfway before it stops and stays"

"1" what?

"Half way..." Are you saying it shifts to the half way point of the cog set (#4 cog, the middle one of a 7 cog set) OR are you saying that the chain tries to climb up on the second smallest cog but doesn't make it over and over?

Among the various reasons the second suggestion I ask about can happen is due to wear (the guide pulley flops about, the chain is totally worn out, the cog teeth are so rounded off they don't grab the chain, the der has so much slop in it's various pivots). Or the cable isn't properly adjusted or the amount of open chain between the guide pulley and the cog's underside is so large that the many links just slop over and the chain's plate doesn't engage the next cog's teeth (and one way this happens is if one of the der pivots is seized and won't let the upper pulley to track just below the cog).

But when you find out what's going on do let us know. Andy

Try unscrewing the adjuster knob a half turn or so where the cable housing meets the rear derailleur. If that helps, but there's still an issue, do another half turn or so.

If your bike is sort of new, this is almost always needed after a while. Your cable housing settled in, and you need a little more tension in the cable. Just a guess, playing the odds.