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Well, I guess I have had the dreaded water pump seal failure on my '90. I have coolant in the gear box and a combo coolant/gear oil coming out the vent into the air filter box. Yeah, me.

Anyways, after doing some research here and looking at the manual, it looks like I need the following parts...

seal(s?)
bearing
water pump cover gasket
side cover gasket

Is this right? Also, I read that I could use the '91+ dual seal setup with all the other '90 parts. Is that correct?

I'm really hoping I don't need to replace the shaft (haven't torn it down yet) as that thing is $56 by itself! If someone knows where to get it cheaper please let me know.

As always, any help is appreciated.

Yes, use the 2 seals from the 91+ with the rest of your 90 bits. Teh bearing bearings probably could use replacing since you'll be in there anyway. Sounds like your parts list is pretty complete. No worries, it's a really easy job.

I had the same problem and i just replaced the mechanical seal that about it. the shaft and bearing are reused and now last me 7 years since. gasket are a must to replace.

Good deal then. Thanks for the confirmation. As for the bearing, might as well replace it while I'm already in there. It is a 20 year old bike afterall!

Well, got it all apart yesterday. Looks like I'm going to have to replace the shaft as well. Oh well, Service Honda has the shaft for $38. Hopefully the parts will get here soon!

BTW, everything else looks real good. I couldn't see any noticeable grooves on my clutch basket or anything else bad.

Well that's good. My basket is grooved to hell. Still works though, at least for now. It definitely drags a bit when cold, but that's the only ill side effect i've noticed. I'm holding out on filing it smooth again as long as I can, since that will only last a little while and then it's forking over serious cash for another basket. I imagine filing them more than once would be a very bad idea.

I got it all back together and all seems well with the waterpump. More of a pain than I thought it would be. The inner bearing didn't want to let go of the case and the new outer bearing had to be pressed in where the old one just came right out. Eh, it is done and working so I'm happy I can ride again.

Now if I could just get the damn vent tube to quit pumping gear oil into the airbox then life would be all good.

Crank seals?

If he thought the water pump seal was a pain, he'll laugh at that after doing the crank seals.

Mr. Wibbens wrote:Crank seals?

That is what I'm afraid of. If I have to go into it that far then I might as well do a complete rebuild IMO. Well, riding season is just about done here in Southern AZ so maybe I'll do it anyways. The bike is 20 years old and I'm sure it wasn't maintained by previous owners.

Pull the stator cover and check for oil there. Usually the LH bearing/seal fails first due to the weight of the flywheel. There would be telltale signs of old fuel mix there. Also if your transmission oil smells of gas, that's a pretty sure sign. Or if the exhaust smells like tranny oil, another sign.

So, about how much is rebuilding the bottom end going to cost me if I do the work? I'll send the crank off to RB but everything else I should be able to handle. I've done several complete auto rebuilds and a few top ends on my old RD's so I think I should be capable.

Also, what special tools will I need?

Gonna need a case splitter. I ended up borrowing one from a local guy, who answered an ad on Facebook that I started. I also had an ad on Craigslist asking to borrow the use of a splitter, 3 more people answered that ad

Whatever you do DO NOT PRY IT OPEN!!


Cost just depends on where you get your bearings and seals

Bike shop is gonna cost a lot more than a bearing supply house

I have a buddy that got all my bearings at cost, so it only ran me about $50

Thanks for the info and I promise I will NOT pry it open!

Tucson pretty much sucks for doing just about anything other than riding. I probably would have to drive up to Phoenix to find an bearing supply shop. I will probably be using Service Honda to get all my bearing as they have had the best prices, so far, on OEM parts. If you guys have a better place please let me know.

You'll need a flywheel puller, a way to get the case back together, like a press or crank installer tool, and maybe a clutch holder tool. I don't know for sure if the KDX needs a clutch holder or not, but the YZ did. You might be able to use a strap wrench. I also use a piece of aluminum bar stock at times to jam the primary in order to loosen some things. The YZ used 3-bond between the case halves. It's really so simple even a Wookie could do it, just make sure your tranny shafts are lined up and going into their sleeves before squishing it all together. Check all your tranny bearings though, especially since yours had water in the oil.