I read once about a guy going round the world on his CX500, he washed his in petrol and then brushed it with clean engine oil.
A lot of people say I wash mine in ABC and spray XYZ on it without problem but unless you pull the engine apart and measure it, it could be close to failure.
The thing is most motorcycles do such low millage any problems wouldn't show for years or maybe multiple owners.
K&N give their filters a million mile warranty and they should only need cleaning every 30 to 50,000 miles, a lot of the time you can get way with just knocking and brushing the dirt out of them and re oiling.
Mine was clogged up from brand new after 7000 miles!
As was pointed out to me we keep suffering after effects of other peoples sand storms, volcanic dust, etc, which will obviously clog anything up.
I obviously used the K&N recharge kit first time up but found the cleaning spray a bit feeble so was wondering on alternatives that wouldn't damage anything.
Worst case scenario if it ends up looking ropey i'll simply bin it, but I think now after reading Fazerider's comment i'll give the washing powder a go next time.
You never know, a bit of Daz might clean it up whiter than white and make the bike smell nicer as well.
I'll still use the K&N oil for it though.