Vernon,
In general three causes spring to mind for a rattling top end:
1. distribution chain worn. Can be checked by first removing tensioner spring and then removing the tensioner. Count the number of notches on the extended part of the ´piston´. Total number is 18, if towards 15 are exposed it´s a good idea to replace the chain anyway. Costs in Holland abt. 80 EUROs, non-original. No gaskets required.
2. Piston worn and tilting; however not likely because no sound above idle. Check by removal and measuring. Remedy is rebore and oversize piston. Piston abt. EURO 80, rebore 40.
3. Excessive valve clearance; again not likely as the sound goes away at speeds above idle. Check by adjusting clearances.
Succes!
Auke
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