I've only got about 1300 miles on the bike, so no, I didn't change the chain. The sprocket is designed for the same pitch chain so it works fine with the stocker; you just have to move the wheel back with the chain adjusters about 3/8 inch to make up for the smaller diameter sprocket. The chain slack at the midpoint between the sprockets is supposed to be between 1 and 1.4 inches with the bike on the kickstand.
As far as the changes in rpm at a given speed, I didn't experience any huge difference. The way I understand it, changing the rear sprocket to a 43 tooth actually goes a long way in correcting the error in the speedometer. So, I am still seeing about 5000 rpm at 70 mph but I am actually going 70 now instead of 65 or whatever I was actually going before the change in gearing. You follow that? It is a little hard to get your head around but I think that is what is going on. And I haven't had it on long enough to tell any difference on fuel consumption. It definitely has longer legs now in first(don't have to shift half way across an intersection) so I imagine you would see a corresponding reduction in your time off the line if you are into drag racing, which I am really not. Hope that helps! J.
Last edited by Jungmann1; 09-08-2009 at 04:39 PM.