The left exhaust pipe is a dummy and contains the cat.

Oh. So what do folk do to get rid of the little blighter? Aside from going the rote of an aftermarket system??CheersTracy

The 650 is the only bike in BMW range that has the Cat inside the exhaust canister itself (and it's on the left hand side of the bike as you sit on it). For the rest of the range, the Cat sits between the header pipes and the exhaust system so replacing the exhaust with an aftermaket pipe like a Remus or Akrapovic is not going to be a problem environmentally speaking. I've done this with my HP2 and geez it sounds good.On my Dakar, I've taken the OME exhausts off and replaced with a single Staintune unit. I did this for two reasons; a) it reduces wieght, by about 5kgs; and b) mid range performance is a bit better, which is what you want for adventure riding.If your not looking at replacing with an aftermarket exhaust then the only other option is to rip open the OEM and remove the Cat (not a recommended move and probably not a very good look I'd have thought, but each to their own).You do need to decide though why you are doing it. A catalytic converter is just a device that treats the exhaust before it leaves the engine and removes a lot of the pollutants now being attributed to global warming etc. etc. (different debate so let's not go there). Legislation in Europe is primarily responsible for all BMW (and other Euro brand) motorcycles being equipped at manufacture with catalytic converters these days. The GS is equipped with a three-way catalytic converter. "Three-way" refers to the three regulated emissions it helps to reduce -- carbon monoxide, VOCs and NOx molecules. The converter uses two different types of catalysts, a reduction catalyst and an oxidation catalyst. Both types consist of a ceramic structure coated with a metal catalyst, usually platinum, rhodium and/or palladium. The idea is to create a structure that exposes the maximum surface area of catalyst to the exhaust stream, while also minimizing the amount of catalyst required (they are very expensive).The reduction catalyst is the first stage of the catalytic converter. It uses platinum and rhodium to help reduce the NOx emissions. When an NO or NO2 molecule contacts the catalyst, the catalyst rips the nitrogen atom out of the molecule and holds on to it, freeing the oxygen in the form of O2. The nitrogen atoms bond with other nitrogen atoms that are also stuck to the catalyst, forming N2. The oxidation catalyst is the second stage of the catalytic converter. It reduces the unburned hydrocarbons and carbon monoxide by burning (oxidizing) them over a platinum and palladium catalyst. This catalyst aids the reaction of the CO and hydrocarbons with the remaining oxygen in the exhaust gas. The third stage is a control system that monitors the exhaust stream, and uses this information to control the fuel injection system. There is an oxygen sensor mounted upstream of the catalytic converter, meaning it is closer to the engine than the converter is. This sensor tells the engine computer how much oxygen is in the exhaust. The engine computer can increase or decrease the amount of oxygen in the exhaust by adjusting the air-to-fuel ratio. This control scheme allows the engine computer to make sure that the engine is running at close to the stoichiometric point, and also to make sure that there is enough oxygen in the exhaust to allow the oxidization catalyst to burn the unburned hydrocarbons and CO.So, if the environment is not your primary concern, unbolt your exhaust and part with it - the catalytic converter is inside. The amount of noise you get will depend on the pipe your replace the original with, most manufacturers of aftermarket pipes give you a dB rating – usually around 88 or thereabouts with some for of restictor so as to keep you legal on the road.Fuel consumption should not change a lot as the oxygen sensor mounted further forward on the header system is still using information to control the fuel injection system and the amount you burn.Hope this heplsGarry