Checked at 12000 km and 18000 km. and I found the gaps increasing too like Engenia.Mine have been fairly close to spec. since new, but I found the gaps increasing. Normally they go the other way.
Turns out, the shims are a little too soft. The valve stems had hammered an indent into each shim! Not seen this before, and it stuffed up my calcs for new shims. Had to make a couple of orders before I could get it right.
Did it for the first time at 30,000 km.
email Chris at Precision Shims Aust. He's very good. Will even match up an unusual size. Normally they're in increments of 0.05mm, but he's sent me a specific size in the past....It seem true that shims are too soft (have indent as Engenia wrote) so the gap has increased.
What kind (from where) of shims you have used? I need to change them all.
First, sorry my bad english.email Chris at Precision Shims Aust. He's very good. Will even match up an unusual size. Normally they're in increments of 0.05mm, but he's sent me a specific size in the past.
The diameters are 7.9mm (0.1mm under standard), but that's not a problem.
Why are you changing the fixed (front) guide? It's only the moving (rear) guide that needs changing.