Finally changed my 17T stock to an 18T yesterday. Went riding 2-up today to check it out. It made a LOT more difference that I thought from reading all the posts. It didn't hurt the start off in first, but did take a bit of quickness off fast starts as the gears get noticeably taller. BUT, there is absolutely no tendancy to want to sift up to another gear anymore. 5th is more like an overdrive now for use above 45 mph. Before I was getting about 50 mph at 3000 rpm and now it hits 57 mph at 3000 and it about 10 mph faster at 4000. You can even downshift at 70 and take off. I used to ride in 5th a lot around town where now I find myself shifting more 4-5, 5-4, etc. I think with the added hp from the jets and exhaust, the 18T is probably right for this bike unless you just have to leave everyone off the line. With the noticeable difference at hwy speeds it should get my mileage back to where it was before all the mods. Again, I was surprised how much difference going up one tooth made. I think I'm staying here for the long haul. I would never consider to up to a 19T as you would be giving up too much. I have an overdrive now, it would be crazy to go higher unless you did nothing but hwy riding. Also, it wasn't hard to do as I followed Pat's directions I printed out. The only trouble was getting the sprocket nut tightened back to 132 nms. I ended up going by the shop manual method of putting the chain on and holding the brake while also in gear. My advice to anyone with an America and a stock 17T, you should try it - especially if you've already boosted the power a bit from stock. My guess is - you'll like it better.
