I want to delete 90% of my keywords for a test BUT if the test doesn't work well I will add them back. Will it hurt the quality score or anything else within google which affects the amount of traffic I would get?
Yes, if you delete the keywords and add it latter it you hurt the Quality score and will erase all history (impressions, clicks, CTR% per period). why do want to delete it? Try other solutions: Create a blank ad group and use the tools>copy keyword /ad group to duplicate the keywords - so you can delete the entire ad group that you want to preserve and revive it latter with no hurt.
With this procedure will be possible to make your test and rollback with the previous state. But if you copy it to a new adgroup it'll not copy your quality score also. new group's quality score will be rebuilt again after some days.
so if I setup a new ad group it will take a few days before I will really see the actual traffic I should be getting? if so about how many days at most would you say?
the traffic for the search network will be up within just 3 hours - but it will not be 100% as before due to the quality score is not so good. it'll take some days to the quality score to be up again but maybe the influence of it is not so relevant. The traffic for the content network (if you have its option enabled) will take 2-5 business day as your ads need to be approved.
In my experience it can take even longer than just a couple of days to regain a quality score (one particular ad-group never recovered 100% after deleting and later recreating keywords). I recommend not deleting keywords unless they are performing very bad.
I remembered a trick that you can do also: you can disable individual keywords by setting its bid value to minimum: keyword ** 0.01 instead of deleting it, this will preserve its quality score as the quality score is at keyword level. To reactivate it latter just remove the ** 0.01
I can't find an option in adwords where I can pause the keyword itself? is there such option? if so wouldn't that affect the quality score?
no, know one knows how the Quality score Algorytim works - no one knows if a inactive word is considered paused or running for the quality score calculatuion. Sorry.
I wish you could pause a keyword...that would be very handy. Im testing multiple ad groups atm, and since im on a limited budget i cant really run all my keywords at once. So a run half of what i could to get decent idea of the impression rate for various phrases. Guess ill just gradually work my way through them until i nail the good ones. Its gonna take a while...weeks probably.