[squirrel_hunter]

They all knock sir.

However there is nothing wrong with replacing the fork oil. Often overlooked and will transform the handling of the bike if there is standard tired stuff in there. To do it properly you will have to take the forks off to pump the old oil out, I doubt very much using a syringe from the top with the forks still fitted will get the mess that is likely to be in there out.

Refill with new fork oil, I'd not recommend using engine oil. There is more than likely a technical explanation as to why fork oil is produced, but that is one I sadly do not posses. 10w is standard, 15w is recommended as it stiffens the front up a bit to stop the front diving so much under brakes.