a friend of mine had terrible trouble with a box recently, would eat clutch release bearings in 150- 300 miles. It turned out to be the plastic bushes for the clutch release arm on the BE3 were the wrong colour. There's white and yellow.     In the picture you can see the difference. In reality what happens is the clutch fork is not centred to the shaft but is about 5mm off centre, result, it's wrecks the clutch bearing!   Part No's i've seen bandied about are   2175.20 and 2175.21 but not sure if this is for yellow or white.   So be careful, use the right ones, yellow and white are not the same!