I have a 03 Z400 that has about 6 hours on it. I installed a Yoshi pipe and the bike ran fine the next time out. It then sat for about a week before I started it again and it would barely start. When it did start it wanted to die after the idle came down. Now I have to keep on the throttle so it won't die and when I try to ride it there's a lot of popping coming from the exhaust, kinda like a lean pop that a car would make. Am I correct in assuming I need to be jetted? This is my first quad (bought a Honda 400EX the same day) so I'm brand new to this. Any help is greatly appreciated.

 

If you changed the Full exhaust I would check the header bolts for even tightness. Then I would check the hose that comes from the top of the gas tank to your handle bars for some debris that may have it blocked. I would check those easy items first then I would go for the jets.

 

I agree with RaptorOwner, it sounds like you might be sucking air some place, or possibly the choke is partially on. If you changed the pipe you may have to rejet also.

 

You've opened up the exhaust, but have you opened up the intake any? removed snorkle, airbox lid, added a k&n, etc.? Most piped Z's are runnin' that way, along with a 155 main.

 

Just 6 hours and already a full system yoshi? Your quad isnt even broke in yet. Like craZ400 said. You also need to rejet and definatly open up the intake. At least remove the snorkle. Id also check the header bolts like raptor owner said. If it were me i would run the quad stock for at least 10 hours and change that break in oil before rejetting. This is recomended but i guess 6 hours is close enough.

 

Thanks for all the advice. As I said I'm new to the sport so I wasn't aware that I should run the bike for 10 hours before adding the pipe. I'll check into what you suggested and thanks again for the help.