Performance problem, 06 pipe on 07 450

[duzz10]

My 07 exhaust system was beat up pretty bad so I just replaced it tonight with a new 06 system. Fired it up to check it out, and after it was warm when I snap the throttle it repeatedly falls on its face or dies. There were no problems before. I did just clean my air filter, and oiled it pretty heavy. I don't know if it is from the filter, or if it needs tuned to the 06 system. I did compare them, and the 07 has a bigger diameter header, and a smaller diameter outlet. The 06 has a smaller diameter header, and a bigger diameter outlet.

[2grimjim]

Yup...........the smaller diameter on the muffler will affect jetting, try moving the needle up before messing with any of the jets.

[todds924]

Yup...........the smaller diameter on the muffler will affect jetting, try moving the needle up before messing with any of the jets.

Jim, so what your saying is the smaller diameter headpipe will make the bike run leaner? I kinda noticed that on my 08. I put on a pro circuit Ti-4....I got a good deal on it............. and it is the same spec pipe as for the 06 and 07. The headpipe is way smaller than the stock 08, which is huge. But i ran the stock jetting and only bumped my fuel screw to 2 1/2 turns. It ran pretty darn impressive. Until this last weekend at the races. I ended up using some Ultimate 4 race gas...what a mistake. My bike was spitting flames like the Munster Mobile. Any how, back to pump gas and maybe a bump on the main jet to a 163 or 165/ and i will try a 48 pilot, back off on the fuel screw a bit. Like i said, with the pump gas it felt really close. Any thoughts?

[2grimjim]

It's hard to say, but from the symptoms you are describing you have a lean condtion and moving the needle up doesn't cost anything. You may have to fiddle with the pilot jet, idle screw, and maybe a different basic diameter on the needle (4th digit).

If you move the needle up and your hesitation goes away AND you don't have any breaking-up/gurgling @1/2 throttle you have hit a home run.

[todds924]

It's hard to say, but from the symptoms you are describing you have a lean condtion and moving the needle up doesn't cost anything. You may have to fiddle with the pilot jet, idle screw, and maybe a different basic diameter on the needle (4th digit).

If you move the needle up and your hesitation goes away AND you don't have any breaking-up/gurgling @1/2 throttle you have hit a home run.

There is only a little break up on the top end. Everywhere else feels good, just the popping on decel coming down from long straightaways. i am hesitant to bump the pilot jet because my bike starts first or second kick when very hot.....I like that.

[2grimjim]

Jim, so what your saying is the smaller diameter headpipe will make the bike run leaner? I kinda noticed that on my 08. I put on a pro circuit Ti-4....I got a good deal on it............. and it is the same spec pipe as for the 06 and 07. The headpipe is way smaller than the stock 08, which is huge. But i ran the stock jetting and only bumped my fuel screw to 2 1/2 turns. It ran pretty darn impressive. Until this last weekend at the races. I ended up using some Ultimate 4 race gas...what a mistake. My bike was spitting flames like the Munster Mobile. Any how, back to pump gas and maybe a bump on the main jet to a 163 or 165/ and i will try a 48 pilot, back off on the fuel screw a bit. Like i said, with the pump gas it felt really close. Any thoughts?

The ultimate 4 will require major rejetting...........

If your motor is fairly stock, fresh 92 octane works fine.

The problem with running race gas is you have to jet the bike specifically for it. You'll have jetting fits if you try and switch back an forth from race gas to pump gas...........it's like switching exhaust systems.

If you want to run race gas you need to keep a notebook on which jeting to use with each type of fuel.

[2grimjim]

There is only a little break up on the top end. Everywhere else feels good, just the popping on decel coming down from long straightaways. i am hesitant to bump the pilot jet because my bike starts first or second kick when very hot.....I like that.

You need to drop the m.j. down if you are breaking up on the top. I'm assuming you have the throttle wide open when you experience the breaking up at high rpm.

If the bike starts easy and has good throttle response don't mess with the pilot jet or idle mix.

Don't worry about the popping on decel.

[2grimjim]

It sounds like your jetting is fairly close, just try moving the needle up and go down one size on the main.

If you didn't have any of these problems before you changed the exhaust your not off by much.........don't make any drastic changes and make only one change at a time between test rides.

[todds924]

It sounds like your jetting is fairly close, just try moving the needle up and go down one size on the main.

If you didn't have any of these problems before you changed the exhaust your not off by much.........don't make any drastic changes and make only one change at a time between test rides.

Will do!!! i'll lower the needle clip one posistion and let er rip this weekend. Pump gas for sure!!!!!!

[duzz10]

It sounds like your jetting is fairly close, just try moving the needle up and go down one size on the main.

If you didn't have any of these problems before you changed the exhaust your not off by much.........don't make any drastic changes and make only one change at a time between test rides.

Maybe I will try the sme on mine tomorrow. Like I said it ran fine with 07 system on it. Can't be to far off.

[Decreasing Dave]

The ultimate 4 will require major rejetting...........

If your motor is fairly stock, fresh 92 octane works fine.

The problem with running race gas is you have to jet the bike specifically for it. You'll have jetting fits if you try and switch back an forth from race gas to pump gas...........it's like switching exhaust systems.

If you want to run race gas you need to keep a notebook on which jeting to use with each type of fuel.

If I may expand on this....

VP U4 is an oxygenated fuel, meaning that there is O2 carried within the fuel makeup, thus requiring you to run more fuel (richer) for the bike to run correctly. Remember the old addage, "more fuel equals more power".

Lots of the blingy street bike guys like this fuel (at first) because they typically don't run it hard enough, long enough to feel the ill effects of the fuel. They just know that it's expensive (so it must be good) and the bike runs mean with it (remember, "lean is mean"). Right up until they are blowing valvetrain parts out the motor.

Dave

[todds924]

If I may expand on this....

VP U4 is an oxygenated fuel, meaning that there is O2 carried within the fuel makeup, thus requiring you to run more fuel (richer) for the bike to run correctly. Remember the old addage, "more fuel equals more power".

Lots of the blingy street bike guys like this fuel (at first) because they typically don't run it hard enough, long enough to feel the ill effects of the fuel. They just know that it's expensive (so it must be good) and the bike runs mean with it (remember, "lean is mean"). Right up until they are blowing valvetrain parts out the motor.

Dave

Raced the 08 today 0n good ole pump gas. Didin't touch a jet and the bike ran perfect. Didn't notice any difference in performance either.