Hey out there, i recently purchased a 91 CBR 600 F2. It has an aftermarket yoshimira pipe on it. It also has a bit of a stutter i guess you would call it at about 1500 rpms. Once past 1500 it runs like a dream. Im pretty clueless, and ive heard different scenerios about what might be the problem. Just thought i would see if anyone knew anything that could help me out. Thanks in advance...

L8CBR600

 

Yep, they are notorious for that. Seems to come out more when a aftermarket pipe is put on.

A K&N filter and rejet or try adjusting the carbs.