03 sportsman 90, was given to me and was told it needed the carb rebuilt. Ordered a new carb from amazon. Installed it and can get the quad to start but it won't idle for very long or rev up unless you cover the carb almost completely then it runs good. Not sure what the next step should be, any help is greatly appreciated.

 

If this is an afternarket carb then probably the wrong one, common problem when ordering from aftermarket companies. Normally you are much better off getting a good rebuild kit and rebuild the original carb. The instructions in a kit will give you all the settings and adjustments needed. Aftermarket carbs are a crapshoot!

 

Yes as above. Hopefully you have the original carb still. Not to sound too harsh, but did you honestly believe that's a carburetor that, in it's entirety, cost just over double what a good rebuild kit costs would be good?
from everything I have read, the jetting in the cheap clone carbs is WAAAY off, normally the Jets are just way too big, among other issues to do with cutting corners, like simple holes where brass fittings should be....
Get a rebuild kit for the OEM carb. It's not hard to rebuild one. There is a reason they cost hundreds of dollars for a new one.
If you have already binned the oem one, get a used one off eBay.

 

Typically the aftermarket Chinese carbs work ok for smaller, off brand engines but with larger engines like yours your are wayyyyy better off just rebuilding it, or if you want bringing it to a shop and having it rebuilt. An oem carb for something like this could cost you upwards of $300 so just rebuild the orig. and you should be good to go.