I've got one head off at the 998 at the mo, checking clearances and 6 out of 8 are out. Been reading up on this quite a bit and there seems to be a lot of suggestion that the collets wearing can be one of the main reasons for clearances changing. Is it worth changing the half rings for new ones and redoing the clearances before ordering shims? Half rings are reasonably cheap and I'm not in a hurry. 16500 miles. Also is the collet tool absolutely necessary for refitting?
I would say (and his is not based upon any experience!) that it depends upon if clearances have tightened up or loosened. Going tighter would indicate wear on the valve seat and so changing the collets won't help. If you did then you should really check the clearances again after a few thousand miles.
The collets will compress over time and many re-use old ones due to this (if not broken on removal) need to find out which way the clearances are moving to determine if it is collet seating or something else as Perry suggests
One thing I have learnt from my Multistrada engine rebuild is that the valve sits more snugly in the valve seat over time and mileage which closes up the shim gap. I am told, if you regrind the valves into the valve seat, it is common to required a small amount of material to be ground off the valve stem which opens up the gap again. IMO, collets are expendable and if the cost is acceptable to you, why not replace them and if that opens up the shim gap, all to the good. Andy
Don't mean to buck the trend but did clearances recently on multistrada and they were good to slightly over size rather than small.
Have a close look at them with a magnifying glass, and see if they are deformed on the outer edges (small lip). I change them all every time I do the shims, but the bike lives on the track. This usually pulls the clearances to within tolerance. There are high quality alternatives available.
Good advice comrades. How about that tool, or will letting the rockers snap a few times seat the half rings?
Cool. Opening clearances are tightening, closing clearances are widening. Will have a butchers at the collets before progressing.
