Water pump disaster

Well, I changed the oil in my '98 YZ400 and noticed the weep hole for the water pump spitting some anitfreeze out. So, after researching this on TT I ordered the appropriate seals and o-ring and finally got them today. I removed the pump cover, had no problems and thought "this will be a quick easy fix". The impeller showed only 10 lbs of torque per the manual, so I started easing the socket wrench to take the impeller off. I had the bike in gear and was holding the rear brake for some holding force on the water pump shaft. It gave way to the wrench and started spinning freely......not just the impeller, but the shaft too!!!!!!!!!!!!!! BUMMER. Now, I have to remove the right case cover and check out what happened. Hopefully it's just the impeller shaft...

Anybody have something like this happen??


Sounds like you broke the water pump drive tab off of the shaft. The correct way to do this job is always to remove the right crankcase cover, pull the gear off and extract the shaft. Then, replace both seals, the bearing, if it's loose, and if you find a groove worn it the shaft, replace it too. :cry:

Ditto. You must put a wrench on the backside of the impellar shaft while you remove the impellar nut. You may have also damaged your crank end that drives the shaft. Most likely the shaft broke and the tip of it is sitting in the end of the crank. Make sure you get the broken piece out. :cry:

Ditto with the shaft broken but dont worry the shaft is usually grooved aswell so no big deal.

yup. when i thought i needed an impact to get the shaft off i realized i was doing something wrong. make sure you put the wrench on the other side. got lucky and only broke the impeller shaft. :cry:

Well, I finally had the time to take the right side cover off. The shaft is what broke, but the end of the shaft was still inside the hole (the middle of the drive gear)!!! I thought I was screwed.... Thank god for good shop vac's!! Sucked it right out!

I replaced the seal, installed a complete shaft, and put the thing back together. Worked like a champ! I can't believe it took me over two hours, though (ok, I swapped clutches in the meantime, too, and had to disassemble the parts motor to get the shaft and the "new" clutch out).....


Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now