I removed only the end cap of the muffler on my 80/66cc bike kit. Will that do any harm to my engine because of back pressure and all? Or could I just leave it? I still have the baffler (all the other stuff) in though. what mods could I do to the stock exhaust that are ok for the engine? I have the exhaust that has a weld on baffle so unscrewing it isn't an option.