Rejetting with open airbox.

I have two different questions for anyone out there. First of all I recently had a full FMF exhaust system put on including headers, Powercore IV spark arrestor, and a K&N filter with new jets installed. I had my dealer do all the work for me and it sounds great. Only thing is, is that they left the air box lid on, and everyone else seems to reccommend removing it after exhaust mods. Will I need to rejet my carb if I take the airbox off now? The other thing is, is that when I hit high throttle a decent cloud of black smoke comes out of the muffler, is this normal? Thanks

You will need to rejet when IF you remove the lid,,,no doubt about it,,,you'll have to go up 1 or 2 main jet sizes,,,and it will make the bike run faster too. About the smoke I'm not really sure,,,I'm guessing the bike is not backfiring,,bogging,,everything is runnin smooth correct?? How do you know it's smoking can you see it or is somebody behind you telling you it's smoking. What year is your bike,,,has it had good maintance all it's life,,,,I know you asked the question but if you answer my questions these guys out here will be able to help you even more...:D

ANd welcome to the greatest quad board on the net....and nice choice with FMF I run all FMF stuff too...did you get a high-flow header or a powerbong??

Good to meet you Rico. The bike is a 2002. The exhaust work was done at the same time as the ten hour service. So all of the maintenance is up to date. Basically I have not really gotten a chance to ride, so i have noticed this basically when the bike is sitting in neutral and I rev the engine. You know I just can't sit around wondering how nice it must sound. I had to check it out. The smoke only comes out when I do a good high quick rev. Glad to hear that someone else has the FMF system as well. I did not get the powerbomb header, just the high flow. Well met Rico!

Don't know what would cause that?????:huh
I'm sure somebody else will give you some insight,,,have ya called the dealer back and asked them???

Yeah I'd only use 92 or 93 octane gas nothing less,,and not gas that's been sitting around turning to varnish..

What kind/octane gas you run? Does it always do it or just a couple of times when you first wake her up? Sounds strange, hope nothing to serious. I'm thinkin dirty fuel or poor quality, you using a new clean jug? (not rusted or was used for something else) Pull the plug and see what it looks like, (color). If it were something bad like rings that would be a whitish smoke and would smell like burning oil. If it's a brand new K&N I doubt it would be over oiled but maybe just check it out. Keep us updated on any new findings or info. And Welcome to the site, it's a great place for questions and help.

Good point, it only seems to happen when I first start it up. You think it may just be extra fuel of from a little flooding?

By the way, I love this site. I just registered yesterday and I've already gotten a lot of answers to a lot of my questions. Thanks for all the help.

Well there ya go good buddy,,,these 400's are some cold blooded, hard starten,,,funny actin beast when first fired up,,,but once they get warmed up should run like a scalded dog...glad we could help....now send $5 bucks to the webmaster for services,,,,,J/K...;)

[knighttime]

My fohundred was a ***** to start and kept fouling freakin' plugs until I upped to a 42 pilot and 160 main, and tweaked the carb screws. Now, no choke is needed and plugs last. 400's come lean from the factory according to my repair manual.