Have any of you had this happen on a WR450?

Out riding yesteray and noticed a burning oil smell, pulled off the track only to notice oil dripping off the radiator onto the head pipe and the engine's top end became really noisy!!! I thought, oh shiii, I must have lost enough oil to burn up the top end...

What I found was there is a plug on the front side of the cylinder, to the right of where the exaust pipe mounts, that somehow came out.. I think it is on the exhaust side of the valves but not sure. Under idle, the port pulls air in, likely because it opens a closed circuit under pressure. But it also must work in the opposite under revs and blow air / oil by, thus the oil loss.. I found by plugging it back off under idle my suspected engine noise goes away, thank God. Parts book calls it a " Plug ". Weird deal.

I was also using an approximate 70/30 race gas mixture, but I don't think the high octane gas was the cause. Anybody else seen this yet?? Thanks, Dirtstiff. :)

the hole is where the decompressiom system on older wr's went. there's an aluminum plug available through the tt store. it uses the small screw near the hole to hold it in place.

Hey thanks for the quick reply and I'm in the process of ordering one from TT now.. :)

I just got back from a 3 day ride near Silverton CO and had the same thing happen to me. I was just running pump gas (91 Octane) at about 10,000 ft elevation and noticed the same thing. I stopped, smelled oil and saw the smoke rolling off the pipe. I was only able to ride my bike 1 day of the trip. I wonder if I overfilled the oil?

check your crankcase breather hose running down the left side of the motor. sometimes the clamp gets bent and pinches the hose causing the plug to blow out. replace it with a zip tie so it cant happen again. Then buy the tt plug and no worries.

I kind of had this happen on my 06, but i found the oil on my left boot. Problem? that stupid plastic oil fill plug broke. I reccomend on any year changing the plastic cap to a metal one.

You can get them from here. It is a standard Yamaha part. I bought several after mine blew out...just in case.

http://www.powerpartsplus.com/ part number for '03 is: 90338-18064-00 and shown under the "camshaft chain" assembly view

Ah, now if only TT still carried the plugs. I looked for them, didn't see them so I called and was told they no longer make them. Modquad.com has one for a 2004 YFZ450 quad though. I wonder if the heads are the same? http://www.modquad.com/catalog/product_info.php?products_id=876

Yes that one will work. A lot of guys have used an 18mm freeze plug bought at a local auto parts store. Either one is much better than the stock rubber plug.

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