i know how to change the jets on a 400 - but whats this about needle adjustments.. How do you do that? what is that for ... Where is the needle in reference to the jets...

is this something we (your average 'joe' mechanic) can mess with.

Help...

 

The needle adjustment is very easy to change. When you take off the carburetor cap (what your throttle cable goes to) you will find that the long needle is up there with a spring. The throttle cable is actually hooked to the slide, unhook that and take off the plate that holds the throttle cable on. For your adjustment, all you have to do is move the e-clip on the end of the needle to your desired position. Going down with it will richen the mixture, while going up is the opposite. Man, I pretty much forgot exactly where it came into play in your rpm range, but I know it is past the pilot jet range (low rpm) and it goes in conjuction with the main jet. Be sure to put that plate back on because that is what holds the throttle cable from coming off!!

 

i never did take this off - i saw the cable - but was afraid to touch it - since i didnt think there was anything in there that needing messing with.. i guess there is - i hope i dont screw it up.. does anything pop out or fall out - if you're not carefull... anytime i hear cables/springs... i get nervous.. but i guess ill check it out tomorrow..

thanks

 

RVonSand
First let's clear up some terminology..you have three jets in a carb; a pilot jet controlling fuel flow from idle to 1/4 throttle, a needle jet controlling from 1/4 to 3/4 throttle, & a main jet controlling flow from 3/4 to full throttle. Both the pilot & the main jets are removable & replaceable when necessary. The needle jet is normally a fixed jet & not normally replaced. However the JET NEEDLE is removable & replaceable with a larger or smaller taper on the rare occasions it becomes necessary.This jet needle is however adjustable to provide changes inthe fuel mix within the above part of the band (1/4 to 3/4throttle)When the throttle is closed the jet needle rests at the bottom of the carb in the needle jet. Opening the throttle raises the slide in the carb & also the jet needle inside the slide. the position of the needle within the slide determines the amount of fuel entering the carb..the higher the needle, the more fuel and the reverse also. The normal position of the adjustment circlip on the needle is the center slot.
In discussing this adjustment it is usually clearer to speak in terms of raising the needle or lowering it rather than putting the circlip in 1st, 2nd, 3rd, etc positions.In other words, if you're going to raise the needle one notch, there's no question where the circlip is going.. it's one notch down from center
If you take your carb off the bike all this will be much clearer once you get inside it.
I know this is a long answer to a short question, but hopefully it will save you more short questions


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Also, the spring in the top of the carb is a big one, so don't worry too much about losing it. It's the spring that makes your throttle come back or always have a resistance when you push it. It's pretty straightforward doing this task, you don't have to take the carb off if you're only doing this one adjustment. By the way hot shoe, thanks for refreshing my memory on the rpm ranges the jets and needles affect.