Taller gearing for higher speed. Because peak power is just below 9k RPM, having taller gearing is necessary for bikes that make higher HP numbers and want to utilize that power.Hi! What are the benefits of running 20 teeth in front?
I have used only 19T so far and in general, needed to admit 19/57T combo is the usual one to go at tracks with longer straights, but where does the 20T front one give any benefit?
Do you mean you can push the entire sprocket in and out, or do you mean you are able to deflect the sprocket by making it cock to one side? Are you SURE you have all of your spacers in place and that your axle is tightened to spec? The rear axle should be tightened to 90nm (66ft lbs) so if that's loose, it could also result in problems like you are describing, as well as many more...@Formula390 - you are right, and I think the situation where the chain has come off have been mostly caused by the chain wear and least likely due to cush drives.
My observation on 390 cush drives inferior design has been mainly by the comparison of Yamaha R3. R3 rear hub setup looks to be way more sturdy and does not allow any sort of angular movement of the rear sprocket- the cushions are way larger and provide more side support for the sprocket carrier. While I can get the rear sprocket to move sideways some 3-4 mm with hand on 390 then the R3 one feels like welded.