Q. I have an old 2004 BMW R1200GS. Recently I had a test ride on the latest model, which was a lot peppier to ride and felt much better for it.
Having established that I am too weak-willed to go against my missus and spend the savings on a new bike I began wondering if I could stealthily improve my current bike.
What I had in mind was an aftermarket filter, de-cat it and run a freer-flowing end can. If I do this will the ECU automatically adjust the fuelling (It has Lambda sensors) or will it run too lean? Will I need to spend another couple of hundred quid on mapping?
A. BMW GSs from that era are set up very lean to get through emissions and also so they can run on all sorts of lower-octane fuel around the world.
If a Japanese bike ran this lean it would have holes in the pistons, but these engines are over-engineered and in a low state of tune.
The engine only draws 75% of the available air through the standard air filter, so a less restrictive one is a waste of money.
As for a pipe, that would give you 4-5bhp on top. Pump the rear tyre up by 4psi and you’d get a similar effect. Rather than splash money out on aftermarket exhausts that the missus will spot, you will get really good results if you get the ECU remapped.
Hilltop Motorcycles near Mallory Park in the Midlands offers a service where they will match your bike’s engine to one of five engine management maps they have developed over the last two years.
They do a base run on the dyno to get the air/fuel ratio and spot any dips in the power curve, decide which map suits best and away you go. The power hike is normally 15-20%, but it’s not peaky, becoming more linear and rider-friendly.
Individuals pay £360 with a £10 discount if you are a R1200GS forum member, or if five or more of you book together the cost is £330.