YFZ450 Oil System Problem

[rappin_ernie]

Hi everyone,
I recently got a YFZ450 to work on. It starts and runs fine, but it is making a nasty top end noise. Sounds like metal to metal. I pulled the valve cover and checked the timing and chain. I adjusted the timing and tightened the cam chain. Everything looks good, however it was very dry up top, and I think the lubrication system is failing to get oil up top. Once I got it back together, I filled the oil up ( Exterior tank and crank, crankcase was almost dry ) and fired her up. She ran fine but still made the noise. As soon as I rev it up or ride it, oil shoots out of the overflow hose from the little black container up under the plastics on the sub-frame in mass amounts. I think maybe the strainer is clogged and as soon as you gun it to give the oil pump some pressure to get up top, it is backed up and overflows out of the overflow hose. I think the lack of lubrication is making the noise as well. I would check the oil strainer, but from looking at schematics, it looks like you need to crack the cases. Anyone know what is wrong here or what to check before I tear into it? Thank you!

Mike

[Ride1Rob]

You do have to crack the cases to get to the internal screen. But there is a screen that runs through the bottom of the oil reservoir. If that is clogged oil will surely not circulate throughout the motor. Check it and see what you have.

[m36indiana]

i had an 04 that did that, found out the oil pump wasnt working right, ending up changing it , worked great after that

[southernduner]

im having a problem similar to that too. i have the 523 icecube with a high compression piston and all parts are new. ive busted 2 oil reserve tanks and ima take out the box and "T" them all together. ive had test run on the engine and everything appears fine. theres no smoke and it runs flawlessly. just have a problem with blowing out alot of oil. the only thing i can think of is jus from the high compression and all the rpms and power and also added an extra oil sprayer in the enigine. any info would help.

[rappin_ernie]

I found out that it was from gaskets in the bottom end leaking. It is a common problem in the 04-05's. I would split all your cases and surface the contact areas and then put in fresh gaskets. For whatever reason, when the gaskets aren't sealed perfectly, the pressure in the bottom end gets messed up and all the oil is forced out of the overflow. Hope this helps!

Mike