How to measure piston domes, valve relief flycuts, engine cover thickness and other odd shaped pieces that a conventional micrometer or vernier caliper will not work properly on, using a dial indicator and a positive stop.
All you need is a 1 inch (or more) travel dial indicator, and a solid rod or bolt to be used as a solid backup contact point. In the image above I used a long 6 mm cranckase engine bolt clamped in a vise. The backup stop could be mounted in a board or metal plate etc.
The logo area above is at the top of a large radius on the primary cover, you can see this clearly with a straight edge across it. After grinding this logo area down, the engine oil filter cover will fit almost flush with the outer surface of primary cover, instead of the bad mismatch the way they come stock.
This XS 650 engine primary cover is in my homemade checking fixture and I have ground the "Yamaha" logo completely off. These covers are very thick, this one still has .152" of metal in the cover at the thinnest spot. I would have used it all the way down to around .040" of metal thickness left. Depends on the casting porosity of each cover.
On the inside of the stock cover, just underneath the logo, the Yamaha foundry has thoughtfully made the cover thicker in that spot as shown above, there is extra metal in that spot from the casting process.
The rough ground cover images, and the finished polished images are online at this page:
http://www.650motorcycles.com/XSprimary.html
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