The single spark (SS) F650GS is prone to poor combustion particularly at low rpm due to the lean burn needed to meet emissions standards. The dual spark ignition (DS) was introduced on later models to overcome the problems.
The positioning of the coil and the routing of the HT lead can also be a source of missing and hesitation in wet weather with dirt build up on the engine. A solution is shown in the images at the bottom of the page.
There are a number of options to improve the combustion of the early single spark F650GS. Not all are proven but are based on sound engineering and revolve around improving the electrical energy delivered to the spark plug.
Improved combustion can result in less vibration, improvements in fuel economy, torque and engine responsiveness particularly at low rpm. Overall a smoother nicer machine to ride with a more usable bottom end.
The use of dual plugs on the 2005 onward models is at best a stop gap measure to improve combustion while meeting more stringent emissions laws. The dual spark models can benefit from ignition circuit improvements,
The brisk plug fires at a higher voltage than a conventional plug which gives a cleaner spark with less splutter at the start and end of firing.
Plug Life is 35,000 kms. The BMW coil output is above 24kv.
The brisk is a resistive plug so the BMW plug cap should be replaced
with a non resistive cap. The brisk plug works well on the SS GS
BMW use two resistive elements in the SS plug lead, the plug cap and the
coil connector. Each has 1,000 ohms resistance
The direct hit is a peaking capacitor which fits over a conventional plug. The capacitor stores charge until the firing voltage of the plug is reached. This increases the combustion efficiency. It appears the DirectHit may no longer be available.
The DirectHit is designed to fit over a JIS plug (NGK)
My results with the DirectHit and a standard NGK plug give up to 10% improvement in fuel economy. Combined with the Brisk plug up to 20% improvement in fuel economy, less vibration, with an improvement in power and engine response, especially at low rpm.
The enerpulse plug combines a platinum or Iridium plug tip with an inbuilt peaking capacitor. These are the next generation of spark plugs with an expected plug life of 160,000 kms. They can raise combustion efficiency of energy to plasma from less than 10% to 30% or more.
Enerpulse have released a plug suitable for the GS. The HE2RT model meets the physical and heat range requirements of the STD GS plugs (NGK D8EA and DR8EA). It is copper only not iridium.
The HE2RT plug has been fitted to many SS and DS F/G 650GS and the results are very pleasing. Upgrading the injector is even better.
The GS uses a plug with 12 mm thread, 19 mm reach & a flat seat.
Pulstar have a 10mm thread plug with heat range 2 which is NGK 8-9 equivalent. It fits the Husqvarna Terra and proven very successful.
An upgraded Injector as per this pdf with the Pulstar is even better.
Not a lot is known about the electronics of the Plasma Booster, it is a capacitive device to boost electrical energy to the plug.
At $US249 it is an expensive solution. The company has specified both the SS and DS GS's in their applications chart.
More research on this and their other products may be worthwhile.
In general these devices are a waste of time and money on the 650GS, each is problematic in one way or the other, including the PCV and EJK.
AIT Spoofers - BoosterPlug, Accelerator Module are two, they do little.
AFXIED - Lambda Spoofer, not as bad as most but of little benefit
Dyno-Boost - AIT and Lambda spoofer, outrageous unsupported claims
LC2 - Lambda adjuster when run with the Bosch LSU-4.9 and BMSC connection is the only device with possibilities as it provides logging capabilites and allows the BMS to operate as it was designed to do. Really for expert use only.
Build replacement ignition coil mount so ignition coil faces the RHS and a shorter ignition lead as per the pdf below.
The shorter lead works with your choice plug cap with or without the direct hit. It enables removing the lead (just) without removing the cowlings. Detailed Info pdfs. SS Ignition Leads SS Ignition Lead Parts MSD Plug Caps