I have rebuilt my 400 recently with the JE 11:1 piston, TC racing cam, but I still have the stock exaust on it. It runs good on top end, but has a dead spot on off the idle a little bit. It runs fine, 1/2 throttle to wide open, (I've changed the main jet some), and it starts up and idles good too. I think it is the pilot jet, but I don't know what I should try putting in it. The little jet cost $11 from my dealer!! I tried a 42 from the stock 38 and it helped a little, but it still does it. I heard someone once saying that they went to a 50, but I can't remember for sure. I don't want to have to order 6 or 7 of these little jets when I don't have to because they aren't that cheap and I'm just a kid in high school still. I don't really have that much money. I tried moving the clip on the needle down one position, but it made it way too rich. So I know it's not that. The only left is the pilot jet isn't it? One more question too, after I install that pilot jet, do I have to adjust the pilot screw adjuster too? I just left it 2 1/2 turns out which is where it wsa stock and it ran perfect then. Please try to give me some advice. What does everyone else run for a pilot jet in theirs?

 

Nevermind everyone!! I fixed the problem today!! I'm so happy that it is fixed now. I just put the airbox lid up and it ran like a champ. The cam must have made it need more air than it was getting. Anyway, not that anyone replied, but just for anyone who might enounter this problem later.

 

I'm in high school too, and am saving money for a truck. Instead of spending $400(canadian) for an aftermarket pipe, I modified my stock exhaust. took out the baffel and drilled a few 3/4" holes in the internal "baffel"(looks like a plate with a single 1" hole out of it). I put the spark arrestor back in and it seemed to have a bit better power. I plan on rejeting and cutting holes in my airbox lid for more free power(besides jets, which seem a bit expensive) I was thinking of raising the needle(lowering the clip), but it may be too rich for a near stock engine.

you can also do some modes "deeper" in the exhaust but it has to be cut and welded back together with a mig welder. My dad has an electric which won't work.