Section 31 e of the German StVZO sets out the applicability of the EU noise regulations for foreign vehicles, so if the vehicle with those pipes did not meet these then presumably a fine could be issued. The paperwork would set out how it can be challenged; I would guess by filing an objection at the Amtsgericht, or local court, and you would need a German lawyer.

I was in a group all riding Harleys, mine is fully customised, all fully legal and with an MOT. We all got fined for loud pipes, didn’t like foot pegs or grips and mirrors to small.however with no rev counters they just pulled the throttle back in neutral. Fine came through in the post €220. Is it legal for them to fine me and how do you challenge it?

As an experienced UK rider of various bikes, why do you need to fit a non-manufacture approved exhaust system to make more exhaust noise?

Ok I've had noisy bikes, Ducati, Guzzi and many other old heaps when I was young etc but it's not productive is it?

All it does is p*** off the non-motorcycling public to think that we are all a bunch of noisy, oily degenerates.

My last bike before I left the UK was a Hayabusa, on standard exhausts.

Please don't just make more noise - it just encourages the politico's to think up more stringent noise regulations.