wr400 Oil leak, not in the usual place...

So I purchased a 2000 wr400 a few months back. Its been great and a helluva learning experience. But I noticed pretty soon after a couple days riding that it has to have some sort of oil leak. It goes from the full line on the dipstick to about the middle of full and low within a week, riding about 35-45 miles m-f.

Oil seems to be coming from somewhere in front of where the swingarm pivots. I searched and apparently its common for it to leak from a seal behind the front sprocket. But I check that and its fairly clean compared to the areas that are actually wet with oil..

Most of the oil collects on the bottom/rear of the crankcase area. Its not coming from the oil drain plug either as its clean several inches behind it. I also thought maybe it was coming out of one of the several little drain tubes that come down in front of the swing arm. But they actually hang lower than the swing arm pivot point and appear to drain fuel not oil?

Anyone got any other ideas? I fear the actual crankcase liquid gasket has deteriorated to the point of leaking or maybe the right side crankcase gasket? Are there any other common leaks on these engines besides the seal behind the front sprocket? I know the crankcase breather tube can make a mess but I hardly can believe that tube could cause all this.

The Cam cover breather tube runs down the front left of the fram and if you have a bash guard, will be tucked into it so you can't see the end.

Mine always blows oil down into my bash plate when riding and then drips out slowly as it works it's way back (onto my floor when I get home!)

BUT it shouldn't be enough to show up as a noticable loss on dipstick.

Make sure you check your oil level with the bike warmed up for 5 min, then check the level straight away as the true level is after the oil has pumped through the lines and back to the frame. The oil will slowly drop into the sump overnight but that will be an incorrect measurement. WR400's are a "Dry Sump" where most of the oil is in the frame reservoir or being pumped. Not much at all in the sump.

What he said........

If you don't correctly check your oil level, it will look low, you will add more, crankcase pressure will go up, and you will blow the excess oil out the breather tube on to the frame/motor.

Thanks for the replys guys. I have been checking the oil as it says in the manual which is basically the same as what you said. Warm it up (it says more than 3 minutes so ive been doing 5), then clean dipstick insert but dont screw in, check level.

I wil continue to monitor it. I took the skid plate and cleaned the bottom of the crankcase off over the weekend and drove it around on the pavement to try and get an idea of were its coming from. It still looks like its from the right crankcase cover gasket but its really hard to tell as im sure you all know, oil has the awesome ability to cover everything and hide the source.


I know napa and autozone etc. Sell the dye you add to oil then you can trace it with a blacklight but my guess is that even though its fine for auto engines, maybe not so much the wr...

Just to update this: I replaced my right crankcase cover gasket and that solved my leak. It looks like my old one was original and probably removed and retorqued incorrectly at some point. Because at several studs it was so tight it was smashed to the point of ripping the gasket.

I cleaned it up and its been a few days now and Its so nice to have a clean bike still! Too bad I got a nail in my back tire yesterday... guess tire removal is the next thing I learn :D

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