I have a 90-92 polaris sport water cooled two stroke i picked up it runs but after about a 1/4 throttle it wont rev up and backfires any suggestions

 

It sounds like it's running lean. How does it idle? Have you tried cleaning the carb?

 

i did clean the carb and it doesnt idle at all

 

Check for throttle cable play.

 

the reverse speed limiter is faulty. do a search on how to bypass it.
Try holding that overide button. On that bike it may be off on it's own beside the lightswitch and what not un labeled. except for maybe a sticker on the bars but it may have been washed off years ago. push that black rubber button, it will probably run with it pushed.

 

First thing I would do is try a NEW spark plug (properly gapped). Did you change any carb settings when you rebuilt it?

 

did put a new plug in but didnt think about gap what is the gap for a 94 400 sport