Backfire after reving engine

[erynk]

Just bought a 2009 gz250 with only 320 miles on it. Engine would die with zero choke even when hot. I then adjusted the idle speed per owners/service manual and now getting small backfire after engine back down after reving. Any ideas on what to do.

[blaine]

Just bought a 2009 gz250 with only 320 miles on it. Engine would die with zero choke even when hot. I then adjusted the idle speed per owners/service manual and now getting small backfire after engine back down after reving. Any ideas on what to do.

Try some carb cleaner (SeaFoam or Berrymans B-12) Also you may need to do a pilot jet (idle mixture) adjustment. ;) :)

[Water Warrior 2]

Go with what Blaine suggested. The carb is probably all munged up from stale gas and varnish from sitting so long. You should never need the choke except for cold starting and warm up of the bike.

[JohnC]

Or, look for an intake air leak. It could account for all your problems. (I suspect you actually have after fire, out the exhaust, not backfire, which would be back through the carb.) An exhaust leak can cause after fire, but wouldn't account for the idle issues.

[plato1]

Check/replace your spark plug...Mine started to backfire, just before it went out completely......