Only runs decent with seat/fenders off

[2001-400ex'er]

just picked up a 400ex with Sparks 416 kit (11:1, 39mm FCR, Sparks X-6, aluminum airbox with no lid, Sparks intake, Hotcam stage 2, etc). The quad only runs good when the seat is off and its getting a lot of air. As soon as I put the seat on it will idle but won't take any throttle and dies quickly.

Am I running too rich or too lean? The plug looks fine (tan). I am new to FCR's so any help would be appreciated. I've spent a lot of time on the dirtbike forums trying to learn them. It would be nice to know which direction I need to start jetting.

[DragonGunner]

WOW....this is a new one.....with the seat on you would be running rich. So u would have to lean it....like I said, never heard of this.

[Longdong]

Is the seat pinching the vent tube on top of the carb?

[Thumpin440ex]

Seems the seat is restricting or pinching something like stated. There is more then enough of room between the seat bottom and top of the box..



John

[2001-400ex'er]

This has me pretty confused also seeing as how the plug looks perfect. I guess I'll just have to play around with it until I figure it out.

[Blodg]

^^^there is plenty of room with a normal stock setup. Put the seat on and look underneath and see how much room is between the top of the aluminium airbox and the bottom of the seat.

If may be something pinching as others suggested or a rich condition if the seat is restricting the intake of air. What sizes are the pilot and main jets in the FCR?

[Blodg]

Originally posted by 2001-400ex'er
This has me pretty confused also seeing as how the plug looks perfect. I guess I'll just have to play around with it until I figure it out.
How do you know the plug looks perfect if it won't run with tbe seat on?

How the plug looks with the seat off is irrelevant.

[426kidz]

Yeah, I'd say your pinching something. I cant imagine your cutting the air off that much by having your seat on. What air filter do you have on it, have you ever tried it with no filter too see if its an air issue?

[KKiowaTJ]

Another vote for cutting air, Check height clearences between the box/seat set ups. Can you place somthing over the lid to rule out the no or lack of air?

Is there a loose or bare wire by chance that got over looked and is cutting it out? Anythings possible, Good luck either way