Mrs and I went for a walk in Upperford Copse last weekend, it's near the A32. There were many obviously large capacity bikes blatting past, clearly sporting after market cans,
Well it wasn't me, mine is still stock
Thing is, aftermarket cans are bad for bikes because the exhaust system is designed to give a certain amount of back pressure. If that isn't there, hot gasses can escape from the cylinder and burn out the valves.
Also Fuel Injected bikes will try to adjust the mix to try to fix the problem...
Leading on from that why do 125 riders fit loud cans?
Because they think it's "cool" or "clever" or just because they like loud noises. It's not quite as ridiculous as the mopeds that belt around sounding like demented mosquitos, but it's getting there.
(The less said about the cager twats who run a rich mixture and then put a spark plug in their exhaust, the better...
)
Come to think of it what does a loud exhaust achieve that's good for anyone anywhere any time?
Well there's always the "Loud Pipes Save Lives" brigade who think that it makes people notice them more (which makes as much sense as riding around with your thumb on the horn button all the time).
What *really* saves lives is Defensive Riding and them not expecting everyone to get out of their way...