Sportbike engine/trans's have a primary reduction off the crankshaft of around 2:1, and 10-15k RPM redline is irrelevant, the countershaft is spinning roughly the same speed of the stock RZR engine. IDK if you have done the math, 1:1 from my countershaft to the trans input shaft would put 6th gear at about 40 mph, we are going to push the issue and see if I can get 85 with a billet jackshaft that my buddy is working on...basically 2 chains, and 4 sprockets, overdriving a total of around 2.125:1 (85 mph). There's another guy that did this but didn't do a jackshaft, I believe he was 18:11 and was about stock top speed. I am really worrying about overheating the chain, but I will see if I can just buy the best of the best chain/sprockets and if they last a season, that would be awesome. If not, we will have to encapsulate the setup and do an oil bath or do an oil squirter onto the chain.