Getting started

[Goob]

I have a 09400x with k&n air filter an hmf sport series full system well the exhaust hasn't came in yet so I went ahead and took the choke off and put in a 42 pilot so where should I start on the main when I install the exhaust

[F-16Guy]

To be 100% honest with you, I think the choke thing is more trouble than it's worth. I've had mine both ways, and I like it with the choke better. You won't see any real power gains (none to speak of, anyway), and even with a 42 pilot, it won't be as easy to start as with having a choke. As for main jet size, you'll probably end up no bigger than a 155 without any internal engine mods. I would buy a 150, 152, and a 155. Start with the 155 and see how it runs during wide open throttle runs (since that's what the main jet controls). After you get a feel for how it runs doing WOT pulls, try the 152. If it gets worse (less power), go back to the 155 and consider trying a 158. If it gets better with the 152, make a few hard runs and then try the 150. The idea is to start with a main jet that is too rich and then work down until you find a main that makes the best WOT power. You may even considering starting as rich as a 158 if you want to spend an extra $4. If you get down to a main that doesn't improve or gets worse, go back up to the next richer size and that's where you want to be. From there, adjust the needle for midrange throttle problems and the fuel screw for off-idle hesitation or bogging. Generally speaking, I've found that the stock needle setting is great for most applications. The fuel screw adjustment with a basically stock engine and a 42 pilot will probably be in the 1.5 to 2.5 range. I'd say probably about 2.25 turns out from lightly seated.

[BEAVER.989]

Curious why you think the choke mod is more trouble than it's worth. I haven't had any problems.

[F-16Guy]

I just think it starts a lot easier with a choke than without, even with a 42 pilot. The power difference is negligible, and I got tired of nursing it for the first minute or two to keep it running. I like to just hit the button and have it fire right up. It boils down to personal preference, I guess.

[Snipe]

It should fire right up with choke out, its pretty simple and not much to notice on doing it.

[quadrophelia]

I have a 05 400ex stock motor, hmf sport full system, uni air filter, choke intact and airbox lid on. I'm just about sea level and rarely get above 2k. I run a 42 and a 155

[Goob]

Thanks alot guys you helped a lot should I run the airbox Lid on or off hmf recommends off and should I change the needle position any or leave it stock

[Snipe]

lid on or off is prefference if your gonna race take it off and jet if not leave it on expecially if your gonna be hitting mud or water.

[Goob]

K I won't b racing just trail riding so can anyone tell me if I have to move the needle or leave it stock

[BEAVER.989]

Leave the needle alone. You won't have to mess with it until you get into more extensive mods.

[Goob]

K thanks a lot

[Goob]

Now will I need to adjust the air fuel screw and if so how and where is it located lol completley new to this

[buster024]

It's a half moon shaped screw on the bottom side of the carb near the main jet cap (I assume the '09 carb is the same as the '05.......sorry for the misinformation if I'm wrong). There's a special little tool that you can get to turn it without having to take the carb off. Without it or a similar tool, you pretty much have to adjust it with the carb detached and upside down.

[Goob]

Is there something I can use other than the tool to get it off