When modern four-stroke off-road bikes arrived, most featured some sort of shim-type valve adjustment. Screw-type adjusters at the end of rocker arms that we learned on are a thing of the past. Those adjust with a threaded tappet and a locknut. That is a dead-simple way to do the job, but not one well-suited to ultra-high rpm. Most performance four-strokes use a precision steel shim to manage the clearance between the valve stem and a metal bucket or tappet that slips over the valve spring. The shims can't come out, and they offer positive adjustment. The downside is that you need to have shims on hand, or make a trip to the dealer to get some. A single shim is less than $10, and shimmed valves generally don't need adjustment very often. We find it ultimately more economical and time-saving to keep a Hot Cams shim kit on hand. For the price of a few shims, you get all you will ever need. As we have lived with and worked on more varieties of four-strokes, we have learned of some tips and tools that make this job much easier. To check or adjust your bike, wash it thoroughly, clean and organize your work space and dig up your manual.
07 With slack in the chain you can lift the end of the exhaust cam, angle it and lift it out. You should not need to force anything here. Once the exhaust cam is out, start on the intake cam. The exhaust cam has the automatic decompression system, so it can't be confused for reassembly. Set the cams where they will be safe and stay clean until reassembly.
08 A telescoping magnet works great to lift out the tappets or buckets and shims. Sears has one that is shielded with an outer collar so the very end is the only part that is magnetic. Keep track of the location of the tappets; they need to go back into the same holes if they are to be reused.
09 The shims sit in these pockets, but frequently they will lift off with the tappets when you use a magnet. Make sure the aluminum bearing surface (arrow) shows no wear. Engines that have only one bearing on the cam use high-pressure oil film between this aluminum surface and the steel cam. The surface has to be perfectly smooth to work properly.
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