This article may help if your oil turn out to be GREY! And first, excause my bad english. The solution is related to this post: http://www.thumperta...o-coolant-leak/
I bought my 2009 Yamaha wr450f last year. It had only 4200km on speedometer, and the bike looked like new. It is a full power version. I am mostly using the bike to commute to work. No hard driving at all, short trips.
When i bought the bike, the engine oil was black. Every thing looked allright. After commuting to work for a month or so, i checked the oil again and it turned out to be really GREY!!!
I asked forums on the internet for help, and most of them respond that there is water in oil (witch turned out to be right, sort of..!). Their suggestions are:
- Blown headgasket most likely, coolant leaking into the engine
- Water pump seal is leaking into the engine (Note: The water pump cannot leak coolant into the engine oil. The coolant seal is separated from the oil seal on the shaft by an air gap that allows coolant to escape.)
Here is the elemination method i used (i had many oilchanges with GREY oil before i finally got to think of the nr. 3, witch turned out to be the solution):
- Replaced head gasket, piston and rings. Still REALLY GREY oil after only a few days commuting to work!
- Mounted a transparent tube on the radiator and overfilled it with coolant. No coolant at all leakes into the bike.
- Rerouted the breather hose from the electric starter out into free air. Oil went NORMAL again!
In retrospect, the cause of the grey oil problem on my bike is that the "enclosed Y" breather hose system (see images below) has transfered moisture from the head direktly into the engine again trought the starter motors breather hose. Because i almost NEVER drive the engine really hot! The engine never get warm enouht to evoporate on my short 10 minutes trips. My breather hose was producing condensation (i could see condensated water dripping when i dismantled the hose) every time the bike stopped, and poured it back into the engine... It was a big surprise that it would produce that much condensation.
Now, i take good 50km ride every now and then, and the problem has dissapeared entirely. All that f****cking work for nothing... Lesson learned :-)!
Edited by Jon E, March 29, 2014 - 12:46 AM.