I took her out for a ride, And every time I decelerate with or without using the brake, once it revs down to 1200 rpm just above idle rpm...it will give one loud pop out the exhaust. Exactly one... It's not a crackle just one pop. I'd like to know what might be the cause of this, and how to fix it. Also, If I could get one mod to increase horsepower what should it be?

 

Just repaired a Honda 420 that does this, I put it down to weak mixture, probably due to a slightly dirty fuel filter. The fault it came in with was the battery going flat, and it still gives the backfire with this sorted. The only single mod you can do with an EFI bike is to get a "performance" ECU, as the standard one is tuned to the standard exhaust, cam etc, and fitting say, a performance exhaust, would upset this balance resulting in lower performance. Do you really need more power than the standard 750 motor produces?