KZ650 Shim Kit - cylinder head rebulid and swap questions

With the KZ550/KZ650 models, the shims are under the bucket.  Because of this, you want to:

1. Document what shim thickness is in each bucket - together with the clearance you end up with
2. 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.  

Jeff.Saunders wrote:

With the KZ550/KZ650 models, the shims are under the bucket.  Because of this, you want to:

1. Document what shim thickness is in each bucket - together with the clearance you end up with
2. 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.  
 

thanks for all of this. just to clarify, i bought a used head, had everything redone in it, including the seals. now the old head is being taken off the bike, and the cams, etc swapped into the newly rebuilt head.

With a refurbished head, you should be prepared to recheck clearances after 50-100 miles of running..   The valves with settle into the seat slightly causing clearances to close a little.  This is certainly a reason to make sure you opt for wider rather than tighter clearance the first time around.

Jeff.Saunders wrote:

With a refurbished head, you should be prepared to recheck clearances after 50-100 miles of running..   The valves with settle into the seat slightly causing clearances to close a little.  This is certainly a reason to make sure you opt for wider rather than tighter clearance the first time around.
 

Thanks for this advice!