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Sorry I had to learn from your mishap Kyle, but it saved me some major grief also. Apparently DRZ/KLX400s have a potential oil seal failure that can leave you with a destroyed engine pretty quickly.
There is a o-ring and oil seal behind the counter sprocket for the drive shaft. I witnessed Kyle lose one of these seals and dump his oil in a hurry. Ever since then, I have been paranoid, watching pretty close for any signs of a leak. About two weeks ago I was washing up my bike after a 200 mile ride. Sure enough, I could see oil dribbling out behind the counter sprocket. It would be pretty difficult to spot a problem from these seals while riding since the oil dumps out under the bike. About half my ride was on rangeland so I was pretty lucky I didn't have a complete failure in the middle of nowhere (in mud of course).

I made a quick order to Bike Bandit and completed the repairs tonight. The cost for the o-ring, oil seal, bushing and, sprocket washer... under $10. Took me less than two hours of time. I think this was time and money well spent to avoid a complete engine meltdown. Might be a good routine maintenance item to add for bikes with a few miles on them.

I've read about that but haven't messed with it. I'm hoping the previous owner did it sometime during his many other mods. hope...

Mac, I've read about this issue on the DRZ's. Are the replacement seals/o-rings built differently to correct the problem long term, or is this just considered a "wear item" on this model? Is this the first time it's been replaced on your bike?

-Harvey

Nothing different in the replacement parts. It looks like the o-ring would be most prone to wear and failure. It goes on the inside of the bushing, riding against the output shaft. The bushing is loose on the shaft until the counter sprocket is tightened down. There should not be movement on the o-ring unless the counter sprocket nut has worked loose. This would allow the bushing to freewheel on the output putting a lot of friction wear on the o-ring.
This was the case on my bike. I found the nut loose a year ago, no idea how many miles I put on while it was loose.

I've also read issues where the CS sprocket bolt on the DRZ's work themselves loose and you're supposed to locktite them on pretty good. I wonder if a loose C/S sprocket may be the root cause of the leak and if it's kept tight the leak issue would not happen. I'd be interested to know if the guy with the Z you referred to that puked all its oil out because of the seal failure had a loose CS sprocket for any length of time while he owned it. There's tons of posts over on Thumpertalk about this. There is a late model DRZ for sale in my area at what I'll call a "distress" sale price, (read DIVORCE) that I was looking at. That's why the interest.

Take care
-Harvey

PS; you ever had any problem with the water pump leaking on your KLX?

Sounds like the same setup used on the KTM RFS (and I think the LC4s). When loctited, the bolt/nut shouldn't come loose. That said, a friend's bolt (KTM) came off out in Moab in March. Not sure why ... not tightened, not loctited, who knows ... With that in mind I drilled my bolt and safety wired it to the sprocket (which has holes cast/machined into it).

I was the one at Milford that noted the DRZ puking oil ... thankfully I had a horn to toot to get his attention. The oil wasn't dribbling, it was pouring. On a KTM a bad oring tends to dribble and self-oil the chain. Not sure what design difference leads to this differing result.

I wonder how Husqvarna gets this seal as they use a snap ring to hold on the CSS. Obviously a very different design.

I think if the o-ring gets brittle and breaks into pieces, you can get a major oil loss. As for the nut on the counter sprocket, I had someone suggest a fix that seems to be working. After everything is tightened and the lock washer is set, use some silicone adhesive. The DRZ output shaft is hollow on the end. Goop the silicone in the hole and over the end of the shaft and nut.
I like the safety wire solution. I might have to try drilling the nut and sprocket next time I have them off.

I haven't tackled the water pump yet, seems to be another DRZ malady to watch for:
- automatic cam chain tensioner
- counter sprocket nut and seals
- water pump

Not sure exactly how the DRZ setup works, but the KTMs (RFS and LC4) rely on the thickness of the sprocket and a cupped washer to apply pressure on the o-ring. Some of the aftermarket sprockets aren't the correct thickness (too thin) and lead to leaking.

(BTW, in a bonehead engineering move KTM made the LC4 sprockets thicker BUT made the spline pattern the same ... so put a RFS sprocket on a LC4 and you get an auto chain oiler.)

I haven't heard of a water pump issue?
I took care of the ACCT.