Motorcycle Repair: slip on exhaust from 2Brothers racing, fuel mixture, slip on exhaust

Question
I have recently purchased a slip-on exhaust for my motorbike. My question would be is a jet kit required or can I run this with the stock set up.  Second question. I have noticed since i installed the slip on it tends to back fire on deceleration.  Is this a result of a lean bike which requires the above mentioned jet kit or is it a exhaust leak possibility?

Thank you

Answer
Any low restriction exhaust will require a carb rejet, as the reduced backpressure will actually cause the motor to run leaner. The danger here is that lean motors run hot and if not corrected they can burn valves and put holes in pistons - expensive! You will need to increase the diameter of the carb jets to allow more fuel to be mixed in with the air and a richer fuel mixture entering the cylinder. But you should also change the air filter to a low restriction type, too, if you really want to benefit from a low restriction exhaust. The more air and fuel entering the motor, the more power you'll get.

How many jet sizes you need to go up depends on your bike, there should be a reference given in the instructions that came with the exhaust about how to rejet and set up carbs with a low restriction exhaust. A properly set up exhaust, air filter and carb jet upgrade will make the bike perform better and all but eliminate the backfiring and popping on deceleration. Be advised that your gas mileage will drop a bit.