I just bought a 1994 King Quad 300 that the previous owner had a Cobra exhaust pipe installed on it. Right now it is not running properly and I am in the process of trying to figure out why. Does a Cobra exhaust require rejetting after installation? or are they OEM replacements and don't require the rejetting? The previous owner couldn't shed any light on whether the quad was rejetted or not. Does anyone have any experience with Cobra systems?

 

If I was you I would take off the Cobra and throw it as far away from the quad as I could. I have yet to hear of one actually adding power to anything. All they do is make noise. But, since they don't really outflow the stock system, the stock jetting should be close enough to work with that pipe. Most likely someone jetted the quad way to rich thinking the Cobra required it. Run it in whatever RPM range (low, medium, high) and kill the motor and check the plug. You want a tannish-brown color. Most likely it'll come out black. That's my guess.