I am very confused. I have a 1996 Magnum 6x6 425 that ran great until last weekend. I take it to the woods and fire it up, it runs great at low speeds but when I give it the gas to go fast it sputters and bogs down. It does not backfire at all. I have replaced most of the fuel lines and checked everything I know to check. If I take the air box completely off it runs great and will rev high with no problems. Put the air box back on and it runs like poo again. It does not appear to be collapsing the airbox in any way. Please help!!

 

IT BOGS DOWN WHEN YOU SIT ON SEAT WITH AIRBOX ON-RIGHT???? BUT NOT WHEN AIRBOX IS OFF-RIGHT???WHEN YOU SIT ON SEAT WITH AIRBOX ON YOU DEPRESS AIRBOX DOWN ON TUBE GOING INTO CARB--THIS TUBE IS LOOSE- TIGHTEN UP TUBE-ANYWAY THAT IS WHAT HAPPENED TO MY 2006 500-MAYBE NOT FOR YOU BUT THIS WHAT HAPPENED TO MINE-NOW NO PROBLEM

 

This will bog down without the seat.

 

someone has got to know the magic. help a brother out!!!

 

Don't know if this will help but will it run on choke? Keep the air box on and when idling pull the choke out while giving it gas. If you can ease into it and rev it up, drive it around, punch it a few times...I've had to do this on mine a few times, seems something was acting up in the carb. It's worth a shot.

 

just tried your suggestion, it does the same thing. If I take the airbox off of the carb completely it works like a champ, put the airbox back on the carb, not filter or any obstructions, and it bogs down when the gas is revved.

 

Check the rubber intakes between the motor and carb for cracks or air leaks, also on the hose between carb and air box. they must be air tight for a CV (Constant Velocity) carb to run right.

 

just a thought . take the top off the carb .there is a rubber diaphram under it pull it out there is a needle valve inside that make sure the E clip is on the needle valve . mine done that once this was the prob on mine

 

any updates? I got the same issues.

 

Hi

I have a 2004 400 sportsman that does the same thing, still have not figured it out! Tried another carb, cdi etc, no change. will run fine with air tube off. any more help is appreciated.