No Martyn, that is another thing all together. I do that by putting in the top guide and then holding it in place with a tube held down by the valve spring cap. If I do not have access to a stepped mandrel for the reamer I sacrifice a top guide by opening up the central hole in it. The other gadget is intended to overcome a problem which seems to becoming more frequent as the bikes get older. That is the lower valve guide becoming loose, which can only happen if the lock ring somehow fails, The valve guide then becomes loose and makes a mess of the hole it is supposed to fit in in the cylinder head casting. In my own case there were no symptoms I had noticed. I took the bike down to do a different job and found no lower front exhaust guide and the lock ring in three pieces up with the valve spring. No! I don't know how it could do that either. In the case of both of the Tilley's bikes they noticed excessive smoke from the exhaust, hence the title of this thread. The idea of my gadget is that if the hole for the lower guide is worn then one has to make a new oversized guide, The problem then is if the thread for the lock ring has been destroyed, There are people who are clever enough to weld up the hole and then re-machine a thread in there and make a new hole for the lower guide itself. They are rare specialists and I personally do not know any. My gadget is a simple mans approach to the problem and seems to work well enough by lasting for years. None has ever caused further trouble yet.