i recently purchased a polaris scrambler 400 and rebuilt the top end...at first when i turned it over it would just turn over till it backfired big time...that was using the electric start...the i pull started it and it started and ran but it backfires intermidantly...then all the sudden it just took off and i shut it off and it kept goin even after pulling the plug wire.....any suggestions might help...im thinking cdi box or carb

 

You don't have to post twice on the same problem! Could be an air leak,running lean condition that can cause a two stroke to continue running,especially if it gets hot.Crank seals leaking,lean carb jetting,etc. You've got basically the same post in the expert section also! Gets confusing. Check the carb out as you said in the other post about it overflowing and backfiring,you can also have a leak down test done,check the compression reading. Start at the basics. Plus these engines can super heat quickly,causing it to "diesel" and continue to run also if you didn't bleed the air from the head when you rebuilt the top end.