in for a head spin. My boss/best friend/mentor has an 01 426. we work in a bike shop and are having the damdest time. he had it stock but it didnt have much bottem end. he got a big gun exhaust package and lost the bottem end compleatly lost some mid but had great top. we ran about 60 different jets through it and finnaly got the mid back. we changed the needle to the fmf race, put hot cams.. Anyways, several years ago I bought a 2001 YZ426F, rode it for a few months, then moved to a city where I couldn't really ride much so it sat for a few years. Last weekend I got it going again (just cleaned carb /fuel tank and it started right up like it literally always has) and am considering moving up to something a bit newer (and lighter.
2001 YAMAHA YZ426F Service Data (Detail) Basic Information Suspension System Equipment Engine System Others. Motor Model Code : J308E Bore (mm) 95 : Stroke (mm) 60.1 : Compression Ratio : 12.5.. The 426's are 5 speeds. 2000 models had SS valves, the 2001-02's had Ti valves.. SS is more durable, but there are plenty of folks still running the original Ti valves in the 01/02's.. I feel that my YZ426 is more stable at high speeds in open riding, much more so than a 250 two stroke. I think the bike is very well suited for a taller.