[Brett Lyon]

I recently pulled my 2003 crf450 out of storage where it had been for 6 years. After changing the fluids and plug it started up but wouldn't idle and died when i took the choke off. It pops real loud when i let off the throttle. I ordered a carb rebuild kit and rebuilt the carb but it still runs exactly the same. I don't think its the valves because it ran perfect when it was parked so long ago and it had less tjan 50 hours on it since it was bought brand new. Im looking for suggestions on why its running so lean. Thanks.

[JimDirt]

Welcome to the site !!

It still sounds like a carb issue to me ... I would still physically check the valve lash just to eliminate it positively from the equation ....

What was in the Rebuild kit ?? , and what exactly did you replace ?? ..... Did you replace the O-Ring for the Fuel Screw ??? if so did you get the old one out ??? what is your elevation ?? , what is the Fuel Screw set at ?? what jets are currently (and formerly before the rebuild kit) in it ??? ...... Have you eliminated a loose header connection at the head and where the muffler attaches ??? ....... Have you checked the function of the Hot Start lever/plunger and made sure it is snapping back when the lever is released ?? ,, have you checked the Float Level ??

Also there could be a Electrical issue , you need to check the Stator output as well as Coil function ..... to eliminate them ..... I have seen them go bad just from sitting , so lots of things to look into to eliminate .... but eliminate each item ,before worrying about the next one ,so you know exactly what the issue is ..... but my suggestions would be to start with the fuel system and eliminate each item , just because you replaced a jet , does not mean the passage it is in is not clogged ... also , make sure all the vent lines are clear , sometimes when a bike sits it can get infested with Mud Dauber Wasps , they will pack a small hose full of mud and you won't know it ,blow thru each hose (including the vent line for the fuel cap) to eliminate it , you can use a air hose to blow them each out to verify they are clear ....

[Back2-2]

What you are describing sounds exactly like a clogged pilot jet. Remove & clean and I bet you will be golden. Clean all the pilot jet orifices. The side holes and especially the tiny orifice in the end. Or buy a new one as some people do over cleaning.