The exhaust systems on the F and G Series look the same but there are at least three variants on the exhaust and catalytic converters. The basics of the variations are below.
Two piece system, exhaust on the left, catalytic converter on the right, all up weighs approx 6 kgs.
There is 3kg weight saving in swapping to a single side exhaust system
with no Cat Converter.
A list showing the part variations between the models Exhaust Info pdf
The Dual spark has a 2mm larger diameter header pipe and there are two variants.
2007 models have new firmware (D60B) for EU3 exhaust gas compliance with a modified exhaust pipe, a different type of lambda probe and a modified catalytic converter
Parts Fiche do not reflect the BMW information above, only EU2 parts are shown.
The G Series has the updated components from the 2007 F Series as well as 210E BMS firmware.
The 2010 and later models show revised part numbers for exhaust and catalytic converter as well as black covers.
It appears the revised dual spark header and updated lambda sensor have
retained the earlier model part numbers.
The stainless steel heat shield for the header pipe may not suit everyone and damage to wet weather gear is possible. A better shield may be an improvement.
There has been considerable discussion and instructions for modifying the existing exhaust but the results are not spectacular to say the least and are realistically counter productive compared to purchase of an after market exhaust and either retaining the OEM exhaust as a spare or selling it to recover the expenditure on the new exhaust.
The header can wear at the point under the LHS foot peg, it is worth checking after a fall.
Hot Header Pipe, it can glow - Idle Actuator faulty or needs cleaning, also check 02 sensor.
The RHS needs to be removed first and after removing the bolts it needs to be rocked off the joining tube connecting the LHS. Once the RHS is removed then the LHS can be removed.
The O2 sensor is hard to get at and can be hard to remove, the BMW manual only shows removing the header pipe. Heat and penetrating oil may be needed. There is a special tool BMW No. 11 7 020. Optimoly TA High temperature grease (anti seize) is specified on re assembly.
There are a large number of after market exhaust systems available which eliminate the catalytic converter and can provide a storage tube where the cat converter is mounted. A few of the manufacturers are listed below.
Not all Mfr's have a 650GS specific exhaust but may have slip on pipes which can be used.
When changing exhaust the BMS adaptions should be reset and rebuilt.