Tolerances and leaks have nothing to do with each other, but mixing synth esters with petroleum based oils will make all your seals useless!
Dave, you've been lucky your 5w40 leaked, so you changed the oil. A good flush to the system would have been even better.
Several gearbox failures (synchros) reported in the bike scene have been addresses to the use of a reputable 5w40 oil instead of 15W40 and 20w50 oils, although 5w40 is great for modern engines, but not so good for a gearbox.
(old thread)
That's interesting as bike gear boxes are constant mesh, where do you get this info from???? You can easily change gear up the box very quickly with a bike without using the clutch for that reason.
