When letting off the gas after a long run wide open it sputters... sometimes backfiring. What is the cause of this?

I am running a 165 jet and a K&N Filter on a stock scrambler 500. It is a bout 65 degrees here.

Do I need to go bigger, or smaller on the jet size.

The small drain on the bottom of the carb leaks some gas at the end of the tube, is this normal?

 

sounds like the float in the carb maybe sticking open or not adjusted correctly. i would check that first then see if it still backfires. if it does then go to a smaller jet

 

how do you adjust the float?

 

im not exactly sure on your carb but if you take the carb off, and take the bowl off the carb, when set the carb upside down on a flat level surface, the float should be parallel to the carb body. should be a brass tab that hits the float needle that you can bend to correct it

 

Sometimes backfiring can be cause by you need to adjusted you valves but it should be doing all time on when letting off the gas so can't be that.
<div class="FTQUOTE"><begin quote>The small drain on the bottom of the carb leaks some gas at the end of the tube, is this normal? </end quote></div>
I say try change out the float needle it may be getting old which is not sealing fuel off and 99% of time you don't need mess with float tab when change out float needle when it not doing it job.

 

It sounds like you might be experiencing a backfire due to a lean condition. When chopping the throttle at higher RPMs, if the pilot jet is not supplying enough gas, the mixture is too lean to burn properly and actually pops and backfires. I know it sounds crazy but if that back fire occurs after cutting the throttle at high RPMs, consider going one size bigger on the pilot.

 

How does the plug look?
Is it light ash or whiteish color or if you head pipe is getting real hot (RED) then more than likely you are running lean.
Backfires mostly referes to lean of a situation.