With the KZ550/KZ650 models, the shims are under the bucket. Because of this, you want to:
- Document what shim thickness is in each bucket - together with the clearance you end up with
- Have the next small shim size ready for when you check the clearances next and pull the cams. Then you can complete the work without waiting a week to get shims.
The wear on the valve/valve seat typically exceeds the wear on the cam/bucket - because of this, the clearances usually shrink over time. You never want to set the clearance at the smallest clearance - you'll need to pull the cams all too soon if you do that. I usually try to keep clearances in the mid-to-upper end of the range.
Most aftermarket shims are good these days - there was a batch of bad ones K&L was selling where they were not properly hardened. But that was 5+ years ago.. The ones we sell are made in Japan. The biggest issue with them is the +/- on thickness tends to be a little more than OEM. An OEM 2.50mm shim usually reads 2.49mm to 2.51mm. Aftermarket might be 2.48mm to 2.52mm. That isn't necessarily bad - it just means you want a good caliper or micrometer to measure each shim.
For most of my Z1 shims, I measure them and write the actual thickness on the shim with a Sharpie. This way I can get more clearance consistency across the cam.