How do I adjust the idle for a Briggs 25 HP OHV twin cylinder. It lopes and spits back through the air filter when idling. Hi speed is great.

So you are talking about backfiring, right? You can't adjust away a back fire. You need to start with cleaning the carb and may have to rebuild it if cleaning doesn't cure the issue. I recently did all this and now am installing a new OEM carb to the tune of $200.