New rider - Oil change related question


Just bought myself a used 2003 YZ450F. Enjoying so far.

Just went to do an oil change and realized something is amiss... No oil fill location???

Here me out:

I think the guy I bought it from replaced (for whatever reason) the leftside crankcase cover with the one for the 2002 YZ426F - a bike with the oil fill on the upper frame.

Doing this, I have lost the oil fill port that is supposed to be on the leftside crankcase cover on the YZ450F.

I'm wondering how to get the oil in there now. Can I:

Put the bike on its side and fill in the oil filter location?

Put the bike on its side, open the right crankcase cover at the clutch, and fill oil there?

Fill oil through the DipStick location on the frame?

Any suggestions are greatly appreciated. My thinking is that I'd like to avoid purchasing the spec leftside crankcase cover for +$100 if I can manage without.


^^^ What a 2003 450F should look like


^^^ What a 2002 426F should look like


^^^ My 2003 450F. Note the crankcase cover matches the 426F...


First, I'll directly answer your question. You'll need to follow the procedure for an '03, but lay the bike down on its right and fill through the timing plug. The '03 dip stick cap is too small to be a practical fill point.

But you're not going to like this: You can't put a YZ400/426 flywheel cover on any YZ450. The '03-'05 had a bolt pattern unique to that model run, and the only thing the 426 case fits on is a 400/426 crankcase.

Looking at the rolling chassis, that's an '03-'05. Not the engine.

Thanks for the help grayracer513.

I wasn't able to get the timing plug off, but I removed that side's crankcase cover to fill the oil in without difficulty. Going to be annoying taking 8 bolts out each oil change, but the timing plug was pretty chewed up, almost stripped and I couldn't remove it.

The plug is plastic. Get a new one first, and then cut the center out of the old one, split it, and remove it. Should be no damage to the cover threads.

You understood the point I made about that flywheel cover not fitting a 450, right?

From the 2 different bikes, it looks like (though I may be mistaken) the upper part of the engine is yz450, while the lower crankcase has been replaced with a yz426's.

This is what you're suggesting grayracer513, am I correct?

I'm suggesting it isn't an '03 YZ450 engine. It could be a nearly endless variety of mixed parts, or just a YZ400. The top does look like a 450, though. If it is a 450 cylinder and head (they have to go together), it will say "449cc" on the front of the cylinder near the bottom right corner. It will also NOT have a downward facing stud and nut at the front and rear of the head/cylinder joint.

One dead give-away that you can't see is a 5 speed transmission.

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