These are a few items which did not fit anywhere else or there is only limited information on hand.
The BMW front sprocket cover is subject to deformation and the lower front mount breaks. It also makes cleaning the grease and dirt from the sprocket area difficult. There are alternatives available. The one from Aquatic is the best of them all by far. It fits the GS, Dakar/Sertao, 650X and Husky Terra.
Chain oilers range from low cost gravity feed units, innovative motion or air flow activated systems through to electronic pump systems. Oil leakage is a potential problem on all systems. A pdf of the major mfrs Chain Oilers
BMW advise fork gaiters limit cooling to the radiator but owners fitting
smaller diameter gaiters report there are no problems. The key is to fit
a flat fork brace. The Happy Trails brace is low cost. Shown with
Daystar (L) and Wunderlich (R) Gaiters. Total cost $US60 - $180.
The Wunderlich Gaiters are made by Ariette, model 9981
The front guard flops around a little too much and can eventually break.
The Kiwi solution is a simple alloy brace to minimise the flop.
Use self adhesive sealing foam against the horn enclosure.
The 2010+ G Series has a 14 litre fuel tank. It has been found
that the F Series 17.3 Litre tank will fit, details are not clear.
US Riders wanting additional capacity have also been fitting
the EU fuel tank without the carbon filter and vent valve.
EU firmware is needed to ensure the BMSC operates properly
The BMW fuel filter/regulator is expensive. RTW riders and others have been fitting an additional filter
to protect the BMW filter. The best filter is
the Golan Products mini or super mini washable stainless steel filter.
Part No's: Mini - 60-312C 5/16, or Super Mini - 70-312G 5/16
An alternative is the Sytec Black Anodised Billet Aluminium Filter
Install info is in the Regulator pdf in Repairs/Fuel System
BMW advise guards limit cooling to the radiator but they are needed
to prevent damage to from rocks thrown up from the front wheel.
There are many different guards offered by TT and others or mesh
can be fitted to the existing BMW shrouds as many have done.
Seats are all interchangeable between year models with heights of 780 or 800mm. There is a single police seat and storage compartment available
The BMW seat part number details are in the pdf file Part Numbers
There are a number of spoofers on the market, Booster Plug and Accelerator Module are two of them along with a number of other snake oil products like AFXIED and Dynoboost, dont waste time and money on them, they do little if anything and are unsuited to the 650GS.
While I have not felt a need for a steering damper others have.
RalleeMoto have produced a kit specifically for the Dakar/Sertao.
There may be others as well.
When the catalytic converter is removed the space can be used for a tool tube and still retain panniers. There are a number of commercial units in different sizes. Stormwater pipe is a good robust basis for DIY.
The BMW wheel part number details are in the pdf file Part Numbers