I have a 425 magnum. It has a UNI air filter, AAEN megaphone muffler, white clutch spring, and i moved the main jet to a 150 instead of a 140. When i go wide open throttle it runs worse than it did stock. It is about even in speed with my 160 quadrnner. At full throttle it doesn't sputter it just goes slow and doesn't feel like its revving out. Whats wrong?

 

Main jet is too rich, drop back down 1 size and see if it clears up, if not go one more down. If you are not sure or are doubtful about what I am telling you, try a wide open run again and flip the choke on and I bet it will fall on it's face, almost die. That means it is too rich. Take the lid off the air box or remove the air cleaner it will improve and that also means it is too rich. Let us know what you find.

 

Go back to the stock jet. I have to reset my needle it is leened to far out noy.It is just a trial and erroe deal nobody gets it right the first time.[img]i/expressions/face-icon-small-smile.gif[/img]

 

thanks will stock size run fine or do i need something in betweend 140-150?

 

Stock will probably be fine if you are running rich enough to make it bog like that. Just check your plug and you should be ok. Most times, a pipe change on a 4 stroke doesn't require a main jet change, but not always, just depends on the pipe.

 

i was talkin to olav (i think thats his name) at AAEN he saiud that the pipe sucks the gas outta the carb. He said to try a 150 if i wanted to for more top end. I was just checkin to makesure i didn't screw something else up when i was changing it. Ill go back to stock tomorrow.

 

Yep Olav is good at giving great advise. His jetting recommendations for my machine were spot on almost every time.

 

went back to the stock jet. It runs great now.

 

Good news, glad you got it worked out.