WR450 Water Pump Impeller Removal

I'm trying to put a Boyesen Water Pump Cover (which has a new impeller 75% larger blades than stock one) onto my 2005 WR450 to help it run cooler. The Yamaha owner's manual has a wonderful set of instructions which says "Remove the impeller" and shows a hand holding the old impeller and impeller shaft. The Boyesen manual says "Remove the stock impeller". Nobody provides details about how the removal should actually take place.

How do you get the old impeller out of there? Trying to turn the impeller wheel counterclockwise to unscrew it only turns the entire engine over (and I don't want to break anything). Any great words of wisdom from someone whose done this themselves?

drain the cooling system and oil from the engine and then take of the right side engine cover and water pump cover off. Now use a wrench on the backside of the impellar shaft on the 2 flats provided to hold the shaft from turning while you remove the impellar. :thumbsup:

In order to remove the shaft, you have to remove the right-side crankcase cover, #9 in the diagram. It's listed under "Preparation for removal" under the first exploded diagram. My girl doesn't leak, so I've never had to do it...SC

Now that finally makes sense. You may have a future career writing WR450 owner's manuals...

I just pulled the plug on the opposite side to the crank and held it while I took off the impeller.

wow. I simply applied pressure onto the kickstarter to prevent the engine from turning over and unscrewed the impeller with a socket wrench. Same for putting it back on. It only takes 32 i.p. of torque. But, I'm sure taking the engine apart has it's advantages too.

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