i put a used carbon fiber yoshimura from a friend on my 05 kfx400. he had a 03 z400. the yoshi makes my bike run perfect...idles perfect an revs smooth. i thought full exhausts needed jet kits? am i wrong? should i leave it an just ride or can damage be done to the carb or motor?

 

jet it it will run better and get nore horsepower

 

You won't get the potential out of the header pipe......

As long as you leave the airbox lid on, you can get away without jetting for just a slip-on and see nice gains in the bottom end.

A header change is a waste of time unless you are going to open up the airbox and jet the carb. It won't hurt your machine, but you are not making the best of the headpipe and its extended volume and curve change. In fact you could be losing a little low end torque, since a head pipe will give you more top-end with more air going in....

If you are not going to jet, I would put the stock headpipe back on and just use the Yoshi muffler....unless you cannot do that due to fit issues since it is part of a package deal. In that case if you ride MX or open trails jet it and open the box and let her rip...... the top end gains with a full system are very nice....