Alright.... good news and bad news

For me I guess. And my 99 YZ400F

The Good:

After the bike sat and was apart, and together, and apart, and together 400 times or so.... its finally back in running order. I figured out all of my carb related issues and am waiting on a new set of jets and a needle valve

The Bad:

Also after the bike sat through all of this, i've now got two issues.

[1] Seems like it may just need to be flushed, but my radiator has some black particles floating in it (just looks like black flecks or dirt).

[2] Out of the crankcase breather is coming oil. A fair amount (enough to create a small puddle maybe 1" wide). Accompanying that the oil that does come out seems to have fine strands of milky fluid coming with it, which obviously made me stomach churn. There is also some whiteish smoke coming from my exhaust pipe after its been running.

Things to know:

-I added oil a long time back because it seemed low. I worry I overfilled a good amount.

-I haven't ever changed the coolant. The coolant level also is normal, so I don't know that there is a gasket leak somewhere. But the black flecks in the coolant have me worried that it may be the remains of one that I need to find, and fast.

At this point I'm thinking flushing both the radiator AND my engine oil is a good plan. I'm not sure of the service before I bought it and started working on it (about 18mo ago). Anything you guys can throw out there is much appreciated.

It sounds like a bad head gasket, partially blown that is. The loss of coolant is the most obvious sign. The black bits in the coolant might be what's left of a seal... maybe, could even be parts of the head gasket or carbon buildup around it.. who knows until you check..

Do a coolant flush and make sure you're oil is clean. Fill the rad right up and run the bike for an hour. Let it cool completely and then check the coolant level. It should be just above the inner core when you look inside, if it's lower than that then you have a leak. Remember that even though you filled it completely when the engine gets to running temp then the coolant system must displace coolant because of the hot coolant. This means that you'll always blow a little coolant out when fully filled cause when coolant is hot the volume increases, thus why I said it should be just above the rad core and not right up to the filler neck.

Alright well I will be on my way in about five minutes to pick up some oil to flush with and grab some coolant for after i flush the radiator.

And there is not a drop in coolant level at all, which is why the black flecks confuse me. I will post an update after I flush my fluids and run it for a few minutes.

Thanks again man

btw, condensation can and will form in the header and silencer when the bike sits, especially when it starts getting a little colder out.

If your not losing coolant this may be the culprit

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now