Apologies for the sketchy description of changing valve shims that I posted earlier, I realise now that I didn't explain it very well.
Hopefully this time, with a picture, the procedure will be a bit clearer.
1. Firstly turn the engine over in the normal direction until the valve you are wanting to work on is closed and the lobe of the cam is pointing upwards, away from the valve.
2. Take Tool A with the black knob on the handle (see pic below) and push it firmly between the heal of the cam and the top of the shim in the bucket, then lever the tool downwards compressing the valve spring.
3. With the valve fully depressed, insert the other curved tool (Tool B) so that it sits with thin machined outer edge of the curve on the rim of the bucket and the inside curve of the tool under the camshaft.
4. Hold Tool B in place while you carefully remove Tool A. Tool B should then hold itself in place.
5. Find the slot in the rim of the bucket and insert a sharp pointed object underneath the shim and then lift it slightly (or blowing with compressed air will do the same thing) - remove the shim with a pair of pointy-nosed pliers or magnetic probe.
6. Replace with a new shim
7. Insert the Tool A again and compress the valve spring to release Tool B.
8. Pull Tool A out from between the cam and the shim.
9. Repeat for each valve that needs adjustment.
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