15/39 is what I run - you'll find that it takes your minimum 'trickle around' speed from around 50 kph (at ~ 3000 rpm), down to 30 kph at the same revs. I also found no difference to my top speed - the engine just revved a little harder. I did like how the change closed up the gaps between gears - both for upshifts and downshifts.
Sounds good, I hope to achieve similar results by changing the front sprocket.
And top-speed? I really don't care. Never even tried it. Never do track days. So whatever happens to top speed, I really don't care.
<cough> - I know you don't want to hear this - but FCR's also help low speed running...
Hmm - now I mention it - nothing has made much difference to my top speed - but it HAS made a difference as to how fast it gets there.
I know about the FCR's. I don't have a problem with them either. Great looking carbs and (as far as I know) great performance. They are just a bit expensive to me (€1000 carbs on a €2000 bike...).
Once I know that I'm gonna keep this bike 'forever' then I'll reconsider the FCR's again. But for now they are just too expensive.
And then there's the choke issue. Belgian weather can be rather cold and wet...
Maybe later. I'll let you know!
Besides that; I think I once read an article about FCR and it was said there that if you go FCR for more power at low revs you should go for the 39mm version. The 41mm are better for power at high revs.
Any insights on that anyone?
And yes - cobblestones are bastard things to ride on. Been there.
Double feeling about these things.
They look great in an old town centre. Nice for postcards and exciting at a bicycle race (Paris-Roubaix anyone?).
But hell to ride on, especially when wet.