Originally Posted by SV650rules

If you don't have a stethoscope a long screwdriver is fine, put the handle on your ear and the blade on various parts of the engine to see where noise is loudest, normally piston slap is lower frequency sort of heavier than the rattle of tappet noise, and because the cam lobes operate directly on the valve cap tappet noise is not as common as it used to be ( because there are no rocker arms between cam lobe and top of valve stem ). If it goes away as soon as engine gets warm I would bet on piston slap as I do not think clutch basket noise would be affected much by engine temperature.

As said earlier a noisy valve is a happy valve, nothing more damaging than a valve gap being too tight and running the risk of burning out a valve. If you decide to try and fix it the risk of doing damage or costing a lot of money is probably greater than the risk of engine damage from excess valve clearance, and a few thou less on lift is not going to affect performance - I regularly get piston slap in cold weather on both our cars ( Honda Civic and Jazz ) neither has done excessive miles - but it goes away as soon as engine gets warm so it does not worry me, as I said modern short pistons more prone to piston slap even on New engines than with older longer skirts designs.