WR426F Cooling Continued


Now I think I messed up. I couldn't get the impeller off, PS: the manual sucks. So we tried to rotate clockwise......Snap. Now the impeller turns freely and is no longer engaged with the trans/motor (I am assuming the impeller shaft is broke).

How bad did I mess it up. I stopped working on it, waiting for your inputs.



Kind of an easy fix, however it requires removal of the right side case cover. If this is your first trip into the engine, this is the second easiest cover to remove. You need to drain the oil or lay the bike on its left side, and remove all of the bolts. Pull off the cover, and replace the water pump impeller shaft.

Since the impeller is still stuck, you will need to secure the shaft in order to remove the impeller. There are flat spots on the back side to hold it with a wrench, do that now. Remove the impeller with the lefty-loosey method and replace. Don't forget to replace both seals and the bearing with the shaft.

When replacing the cover, make sure that the dowel with the o-ring is in place and that you removed the broken piece of the original shaft from the counter balance shaft. You might want to replace the gasket as well, depending if you tore the original or not.

PM me if you need more info, I just closed my engine up last night after getting elbow deep into the transmission. I also had to replace my impeller shaft, and it's pretty darn easy once you get the engine open.

The water pump cover has been removed. Are speaking about the bigger cover that includes the water pump housing?

Is the impeller shaft supposed to simply pull out ? There is physically no clearancy between the impeller and housing to slip something behind and catch the flats on the impeller shaft.

Yes, he means the entire cover that the impeller shaft lives in. Once you get that off, you'll see the flats on the inboard end, next to the drive tab you broke. The shaft comes out toward the inside once the impeller is off.

Be sure you retrieve the broken piece from the balancer shaft.

I just zipped mine off with an air wrench...

I just zipped mine off with an air wrench...
  1. You'll end up with a broken impeller shaft one day, just like the OP.
  2. Even if that doesn't happen, the coolant seal only fails all by itself less than half the time. You can't do a very good job of inspecting the shaft for wear without removing it, and you can't replace it with the crankcase cover still in place.

So far so good. The only reason I took my impeller off was to put on the boyesen water pump kit and fluidyne radiators....

This is my first ever thumper and I gotta say I LOVE this bike!

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