If it's ratting when warmed up then it probably is time for a new cam chain, or at least to get a professional to check it out. As I understand it they stretch over time, and just like your drive chain can reach maximum stretch and should be replaced so too with the cam chain. The tensioner just takes up the slack up to that point.
Deefer has been recommended many times and by the sound of it does a proper job with an endless chain at a fair price.
And if it's stinch182's thread I was reading recently then he got a right bargain by removing the engine himself... think he got it changed for a little over £100!?
The alternative is that you take your chances, and accept that if it skips a tooth then there could be serious engine damage. It's one thing to do that when the rattle is just on a cold engine first thing in the morning, but another if it's rattling away when warm. I don't know what happens if it happens when being ridden, could it cause an accident? More experienced people than me might advise.
Or depending on the cost you might consider picking up another lower mileage engine and doing a straight swap. But probably best to get your cam chain changed as at least you know that engine is good in all other respects, and your new one might not be.
I have a bit of a rattle when it's cold in the morning, but it does go away when warmed up and so for now I'm just being careful to let it warm up on the drive and taking it easy for first few miles, and monitoring to make sure it doesn't get any worse. If it does then I am going to address it as they are meant to be enjoyed, and worrying about it all the time can spoil the fun.
Andy
