2003 YZ450F Oil leak please help

4 replies to this topic
  • jakester1967

Posted April 27, 2008 - 10:40 AM


Hey all, I am sort of new to this whole motocross thing and I love it. I bought an 03 YZ40F from a friend and have an awesome time on it,what a fun sport I must say. Yesterday we went out riding and I started to smell oil burning. I could see oil on my right radiator but did not know where it was coming from. Today I pulled the radiator off cleaned everything, and noticed that right above where the exhaust manifold goes into the engine there is a hole where the oil is spraying out of onto the radiator. I can look right into the engine and I dont think this is supposed to be like that. Now there is a screw on the right side of the engine that looks like it is supposed to hold something in there. If it is ike a car I am thinking that there is supposed to be a breather valve there or something. I have been looking for pictures to see if there is supposed to be a plug or something in there. If anyone can help me out with this I would greatly appreciate it. Thanks and safe riding to all.....Greg

  • William1

Posted April 27, 2008 - 11:31 AM


That is a hole for the decomp. Yamaha uses a cheapo plug that from time to time gets blown out. A search here for "Decomp Plug' or 'Decompression plug' will show you many threads. Best of liuck.

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  • MaxPower

Posted April 27, 2008 - 12:07 PM



[COLOR="Green"]you had a cheezy metal and rubber peice in there stock
Install one of these and you will be on your way
Its easy as can be to install[/COLOR]

  • jakester1967

Posted April 27, 2008 - 12:41 PM


Thanks for all of the help guys, I will get the plug in and be ready to ride next weekend. I did go back out and look at my breather line and it is clear from the top with no kinks. I even disconnected it and used low pressure air to blow it out. Thanks again for all of the help....Ride Safe!!!!!

  • grayracer513

Posted April 27, 2008 - 03:29 PM


Here's one of the reasons the Common Threads sticky says "Look here 1st" on it:

Under the heading. "Oil Leak at Right Front of Engine, or
Right Radiator Appears to Leak (Smoke from Radiator and Exhaust), or
Unexplained Open Hole in Front of Head."

We have this:


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