Why you jet your carb

[gscx]

I saw tig wrote an article on how to jet your carb and im just going to explain why you jet it, and sorta help you jet it. Well a carb mixes air and fuel together to put it in your engine, almost everyone knows that. but when the weather changes the mixture of air and fual can change, and since almost all dirtbikes are carburated you have to chabge your jets, the main jet and your pilot jet(the pilot jet doesnt really get changed that often, or never so i wont really go into that part of jetting really) the main jet is what sontrols the fuel flow when you have the throttle about 3/4 open. and the other component of jetting is your jet needle and your jet clip. the clip is what has the most influence of how much fuel is put into the venturi, it works most at about 1/4 to about 3/4 open throttle, so this is probably the most important part of your jetting. and the diameter of the needle is important when the throttle is closed to open about 1/4 of the way. now when i say that this part of the carb works at this throttle opening and another works at this throttle opening im not saying that one part of the carb just shuts off, it keeps on working, but these are the steps at which each componet is most important in relation to throttle opening.now you have to know how to jet your carb in relation to what the weather is. when it gets cold the air is denser, and when it gets warm the air gets less dense. these should be your general rules when it comes time to jet. now the more humid it gets the less dense the air becomes. so if you havent figured it out by now the colder it is and dryer the better your engine will run, if you have it jetted right. a rich engine will run slower and be less responsive to quick snaps of the throttle. a bike that is jetted on thelean side will run faster and have less power, even though it is running "faster". the reason for this is because the less fuel that is put into an engine the less resistance that is put on the piston and the cylinder walls. but since there is not enough fuel the combuston will not be stable and there wont be enough fuel to keep the engine running smoothly at high rpms. so there will be loud popping noses coming from the exhaust when the main jet is lean. also a leaner engine will run hotter and a rich engine will run cooler. so if it about 40 degrees F you should get a smaller diameter needle move the jet clip down one notch on the needle and make the main jet one size bigger. if it is 80 degrees F you should reverse the above process. you should adjust all of these components at once, and not just change one of them, since it is a system and they all work together. and i forgot to add in the element of elevation, the higher you are the less dense the air is and the lower you are the more dense the air becomes. well i hope i helped a few of you with jetting your bike. and if you understand the theory of this you can jet just about anything correctly

[gscx]

oh yea, if someone has anything to add go right ahead

[DobyWillis]

This is also most latin to me but... I think I got ya. I will get mu book out and tear it down to see exacly what size jets I have in and how the needle is set.

For me... I need to see it to fully understand.

Thanks - DW

[gscx]

well what kind of bike do you have

[tigmaster]

You will be fine, its easy.

[razorsedge]

So there is no point in changing your main jet without adjusting your jet needle and clip?

Does jetting affect how your bike starts?

[wr250f95]

yes it does

[gscx]

No im not saying that, its just most people only change one thing, and say its fixed, you hve to look at the whole throttle range and see how its running