How much engine noise is too much?

I understand the yz's tend to have a little more engine noise than some of the other bikes, however how much would cause an alarm to go off? I have an 07 450 and there seems to be a loud noise in the engine. It is not a grinding noise but more of a banging noise, kind of like hitting a metal pipe on a bench. I run full synthetic oil and change very frequently, plenty of coolant, and at times a small amount of a milky substance out of the breather tube. The engine seems to still have plenty of power and starts very easy. Any ideas on where I should start my search?

to help with the noise issue, try to find someone who has the same bike.. then listen to the motor..

The occasional milky drop of oil from the breather is normal, and is a result of the condensation of moisture from the air in the line.

The '06 and '07 were noisier than the earlier models partly because of the aluminum frame. If you have a skid plate, it exaggerates things even more. There's no fix, because nothing is broken. Like Slinky said, check a couple more, they're all like that.

ive got the same bike and i too thought there was something wrong when i first bought it. I wouldn't worry to much!

I had a 2000 426 and rode the snot out of it. I too thought it was too loud, until the crank started going out. Then she lets you know what loud is. When it sounds like a man with a hammer in your motor. Worry then. Till that point ride it like you stole it.

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