All good ideas - 1. What kind of bike do you have? yr / model 2. What kind of style are you going for on the 2-1? maybe we can find a used or budget priced new one for ya As far as hurting the engine, kinda depends on how you modify it. Short answer is if you do a 2-1 and restore original back pressure no harm done, if you reduce backpressure, depending on how much you reduce it, you'll run the risk of leaning out the fuel / air mix which could cause your bike to run hot and do internal damage over time, if off by a crazy amount it may damage it sooner. If you increase the back pressure then you lose power and richen up the fuel/air mix and run the risk of scoring the cylinder walls by having too much carbon build up.