1st of all i'm a newby here.i got a 02 300 ex.i just put a cobra exhaust on it,i also bought the k/n power kit:filter,jet kit and some cleaner/oil,precharger.$140.00 bucks worth of stuff but i'd heard it was worth it."dont think so yet".i changed the exhaust,filter then rode it.it seemed to flutter/sputter in 1st gear at high rpms. then i changed the needle valve and jet from the kit.it still sputters at bhigh rpms. is this normal or what am i doing wrong.i got the 118 jet in.i live in ohio.thanks rodman

 

Hmm, 118 jet huh? I don't know what your altitude is there in Ohio, but the 118 jet is the "high altitude" jet for stock bikes at an altitude above 2000 feet or so. A 122 main is the stock jet for altitudes below 2000 feet. If you still had the stock exhaust and air filter on your bike, and you are above let's say 2000 feet, then the 118 jet would be right. I will try to give a quick explanation.

Again, remember that a 122 main is the stock jet for altitudes below 2000 feet, and a 118 is the stock main for altitudes above 2000 feet.

Air is thinner at higher altitudes, so you reduce the main jet (from 122 to 118 in this case for a stock bike) to compensate for the thinner air by reducing the fuel. If you do not, then you will be running rich, (more fuel than air) and you can foul your plugs (black sooty tip).

Air is thicker at lower altitudes, so you increase the main jet (from 118 to 122 in this case for a stock bike) to compensate for the thicker air by increasing the fuel. If you do not, then you will be running lean, (more air than fuel) and you can burn up your valves and piston (spark plug would show a pure white tip).

Since you have installed a new exhaust which = more air flow, and new air filter which = even more air flow, you are most likley running lean. I would change the main jet from the 118 (if you are above 2000 feet) to a 125 (or a 128 if you are below 2000 feet) and drop the needle jet clip down one notch. Usually the needle jet clip is set to the third groove (stock) and lowering the clip will richen the mixture (more fuel) and raising the clip will lean the mixture (less fuel). The main jet affects the throttle position from 3/4 to wide open, and the needle affects the throttle position from 1/4 to 3/4 open. There is also a pilot jet which affects the throttle position from idle to 1/4 open.

I have a Uni filter, holes in my airbox lid, and a DG pipe with supertrapp exhaust and 12 disks. I had a 130 main, needle clip at slot 4, and a #40 pilot (I think a 40 pilot, whatever is one number up from stock. Could be a 38, I forget right now.) and was riding at about 4000 feet and it ran like crap.
I changed the main to a 122 and left everthing else the same and it ran great. After a lot of experimenting with different jets I have found a sweet spot of a 125 main, needle clip one notch down from center, #40 pilot, and the fuel screw 2-1/2 turns out. This setup works well from sea level to 5000 feet.

I have seen others raise their main jets to a 130 or even higher. I think it all depends on your riding location, style of riding, the kind of pipe, air filter, exhaust, if you have holes in airbox lid, no holes in lid, or no lid at all, ect. All I am saying is that I have found what works best for my setup.

As you can see it takes a little while to get the jetting just right, but when you do, it will really increase the performance with the mods you have.

Ok, so my explanation was not so short after all, but I hope this helps.

 

Rodman I live in Mt Orab if you don't get it fixed let me know,maybe you can bring it over & we will get it worked out .All it takes is a little changing things around.Daryl

 

You are lean. use 128 jet if you leave your airbox lid stock. They run better if they have an inch hole cut in the back. If you run the hole use a 132jet.

 

Hye, where about are ya in Mt. Orab, I live in West Union. I dont know if you have ever heard of it or not but it aint far from you, let me know if ya maybe wanna try to get together and ride sometime.

 

Hey sorry, but i forgot to clerify that my last message was to truck.

 

Ya I know where west Union is,I own some land in Aberdeen.After the weather cools off a bit send me a email & we might get together & ride.You being from West Union should know that if you don't have agressive tires you won't go far in the hills.Our land is nothing but.I run super swampers.Daryl

 

i figured it out.well someone told me.i put the 128 jet back in it and it still sputtered at high rpms.then i noticed while i was in reverse andgave it a lot of gas it did the exact same thing,so i called a dealer and they told me it had a rev limiter in it.thanks for the help guys,lets go ridin

rodman