Gentlemen, I'm a newb at this dirt bike thing. Late 2012 as a father/son hobby dealio I bought an '08 YZ450 from the son of a local shop owner. The kid was an avid MXer. The bike ran well and was cheap so I bought it and rode it throughout 2013 as it was. Riding with more experienced TT'ers I met here resulted in a laundry list of maintenance items that I am completing as I write this. Hence my set of questions. 1: Chain: I replaced the original O-Ring chain (kinked at one point due to bad link installation) with a new X-Ring chain. The replacement chain has a master link. I found that after installing the new chain, the master link got removed by the chain guide when I spun the rear wheel backwards. Do you generally recommend installing the chain without the master link (pressing it on)? 2: Chain Guide: The bike had 14:48 sprockets on it for track racing. While I ride on the track some with my son, I found that gearing the bike down was necessary for enjoyable trail riding. Based on the recommendations of a very good trail rider, I have replaced the rear sprocket with a steel 51 tooth sprocket. After installation of the sprockets and chain the chain guide clearance in the chain guide was definitely deflecting the chain at the sprocket. It also seems tight (narrow) and I blame that for the removal of the master link clip when rolling backwards. But between the tight deflection and the apparent narrowness of the existing guide, the rear tire didn't roll nearly as smoothly as it did with the old crimped chain. So I removed the chain guide and it rolls smoothly, but not as smoothly as it did before. I blame this on the newness of the chain and the new bearings in the rear wheel. I read here that a TM DesignWorks chain guide is the answer, but their website does not mention anything about more room for the larger sprocket or how high I can go with it. Can someone tell me what they have done in this regard? Will a new chain guide allow the master link to roll through backwards without removing it? 3: Sprockets: I replaced both the sprockets with inexpensive steel ones to 12:51. The recommendation was made to go to 12:53, but even with 12:51, I'm gearing down over 20% from the existing 14:48. Due to snow, I won't even be able to test this for a while, and I'm thinking of getting a spare 13 tooth sprocket as well for when I ride on the track or less technical trails with my family. What are your recommendations in this regard? Thanks.