Originally Posted by utopia

If you're familiar with the use of a micrometer it is possible to measure them without the adaptor, but it requires a good engineering "feel" or else its easy to get it wrong. The problem is that you need to measure from the broad flat face that the closing rocker bears on, to the shoulder in the bore (that holds the wire collets). BUT I believe this shoulder is NOT FLAT, but radiused to match the cross section of the wire collets. This makes it easy to get a high reading. The true reading is between the innermost corners of the face and the shoulder, where they meet with the bore of the shim. In practice this boils down to being the smallest reading you can get before the anvils of the micrometer slip off into the bore. .....Anyway, the adaptor eliminates this problem ...it fits against the radiused shoulder sort of like a spacer, and you measure across both, then subtract the length of the spacer. Brancato Engineering OX44 7RW, 01865 891203 make one (they call it a button) £23.50 (see Classic Bike apr '08). I've not tried one. Any such device has to be trusted to be accurate, until you've bought a shim of known thickness to check it against, that is. Some shims have thickness marked on them anyway. And a word of caution.... I've seen respected Ducati mechanics measure shims wrongly using Ducati workshop tools. Set the closers even slightly too tight and it all goes crunch, so with belts off and opening rocker disengaged, check that the cam rotates by hand with no tight spot. AND FINALLY, the wire collets bed in to something like the difference between one shim size and the next, so fitting new ones can restore valve clearances on their own (for a while)....or just confuse the issue. They also bed in one way, so if you put the old ones back in upside down (cos they fit either way) they act like new ones and change the clearances by maybe one shim size. And you need a lens to spot the wear marks, and then its not easy. My advice would be ..measure up, take notes, leave collets in situ, work it all out but don't change anything unless it needs at least two shim sizes, and maybe then just go one size with new collets. Or even try just new collets first....they only cost pence but shims are pricier. Check the videos...the guy from california..excellent. And do use the trick method of measuring the closing clearances via the opening shims...much easier, more accurate and doesn't chew your feeler gauges. Btw, those red kites round your way are stunning, aren't they?