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I have a 2005 450x that has been jetted and I also have a slip on. I recently took it out after the long winter and it is backfiring when I'm decelerating. It also starts hard when it's cold. Any suggestions would be great.

Welcome to the site !

Pilot jet would be the most likely culprit , once the bike sits for any more than 2 months with gas in the carb (thanks Ethanol) then the pilot will be clogged , if you dont have a Jet Cleaning Tool , then just replace the jet , its about $6 , also , have you checked your valves ??

So is the pilot the main jet?

No, the pilot is the primary circuit system jet. It is the jet forward of the maim jet. The main jet is the large center jet in the body of the carb looking from the under side, sticks straight out the body. Pilot is slotted head to remove and has a longer tube that goes up into the base. Very small orifice.

Before you go tearing into the carb try adjusting the air screw 1/3-1/2 turn ccw [out] and see if that takes care or the popping. When a pilot becomes clogged you can hardly start the bike and it pops carries on something horrible.
Air density, temps ect.. require air screw fine adjustments to run perfect.

Hope that helps a little.

So that would be the slow air jet? I new to this carb tuning hope I'm not being a pain. Thanks for your help.

Yes the Pilot is the Slow Jet

Pilot jet and Fuel Screw runs the idle and low circuit (along with main) , the main jet and Needle position run the mid to full circuit

So any lower RPM popping is usually the Pilot/Slow jet , and bogging/stumbling while riding in the mid/upper RPM range is Main jet/needle position

If your going to work on these bikes , the best money you can spend is on a Factory Honda Service Manual for your bike , they are about $56.00

http://www.crfsonly.com/catalog/product ... ts_id/3226

It will tell you and show you with lots of pictures , how to work on everything on the bike , it takes you step by step , its a must if your going to have one of these bikes and work on it yourself