2010 KXF450 water pump rebuild

What prompted me to dig into the pump wasn't what one would expect. I wasn't having any over heat problems or coolant loss. Rather, it was a horrible grinding sound coming from the engine that would suddenly appear, last for a minute and quit. There was a moment when I thought maybe a rock or dirt clod had forced my kick starter back a bit because once the noise stopped I rode a good while longer before it happened again. This was when I noticed the noise coming from the front lower engine case. Well, I loaded the bike in the truck and went home.

Once I pin pointed where the noise was coming from, I realized it was likely the water pump because that was the closest proximity to the noise. The bike was still running flawlessly, so my concern for having some major engine problem diminished.

1 To do an initial inspection, you can remove only the water pump cover. First, though, you need to drain the coolant. Remove the radiator cap before the drain plug. This way, the coolant system will be vented and drain easily. After the coolant has drained out, remove the coolant hose from the pump discharge nipple.

2 Here I have removed the water pump housing. Looking closely, you can see scrape marks on the housing surface and the impeller blades. This damage indicates the impeller had moved outward, colliding with the housing surface. My first thought was the impeller bolt had come loose. This was not the case however. Everything was tight and in position.

Note about pump housing removal: DO NOT wedge anything in between the mating surfaces! To pull it off, tap on it gently with a soft hammer (plastic or rubber) from side to side or top to bottom until you can pull it off with your fingers.

3 On this bike, the upper oil filter cover bolt doubles as a fastener for the outer case, which has to be removed to allow repair of the water pump. Because of this, first remove the oil filter cover, oil filter and filter spring. Remove the filter cover bolts evenly in increments going from one bolt to the other. The reason for this is to prevent the filter cover from being pushed out at an angle, which could cause damage. Normally, the filter cover should remain in position when the bolts are removed. I remove the filter cover bolts this way only as a precaution.

4 When all of the cover bolts have been removed, use a soft hammer to gently tap on the case cover to break it free. Once the mating surfaces are loose, you should be able to pull the case cover off while wiggling it back and forth slightly. You should attempt to maintain the straightest possible position of the cover as you pull it off. Avoid prying in between the mating surfaces at all cost. Straight and even is the solution. Additionally, you don't want to damage any of the oil seals.

Be aware! When the case cover comes off, there is a steel pin that will probably fall out. This pin serves as a shaft for the oil pump gear. The gear will drop down out of location when the pin is out. At this point, there is no need to worry about it, just don't lose the pieces.

5 Here's a view of the water pump driver. Minor damage at the end of the driver is evidence that the water pump shaft drifted outward enough that the shaft actually disengaged from the driver. This explains the grinding sound I heard during my last ride. Fortunately, the damage was very minor. All that was needed was to smooth the surfaces flat with a honing stone.

6 This is an internal view of the right side case cover. Now is a good time to carefully clean and inspect everything. Consider whether or not any of the seals may need replacement while this is removed.

Notice the oil pump gear shaft that I mentioned previously. When I removed the case cover, the shaft stayed in the cover as seen here. This shaft must be removed from the case cover and inserted into the gear and shaft socket on the case side when the case cover is installed.

7 This view shows the inside end of the water pump shaft. All that holds it in place is a snap ring. First, clean everything. Carefully remove all gasket material from part surfaces with the aid of a good razor blade. You must be careful not to scratch any gasket surfaces! After cleaning, remove the snap ring and slide the pump shaft out of the bearing pack. Note: The impeller can be removed from the shaft before or after the shaft is removed from the case cover. The flats on the pump shaft allow for placement of a wrench. It is also ok to remove the impeller from the shaft when the case cover is still bolted to the engine. The engine side pump driver will hold the shaft allowing screw removal.

8 Top:
Water pump bearing and seal bore all cleaned up.
From left to right: Snap ring, back bearing, bearing spacer, front bearing, shaft, oil side (inner) seal, water side (outer) seal, impeller, impeller to shaft screw.
Water pump assembly. From this view you can see that it is possible to drive the entire assembly out from the inside of the case. I chose not to do this for a couple of reasons. 1) To minimize the force needed to remove and 2) to prevent the bearings from driving through the seal bore. I removed it as follows: I first drove the seals out one at a time by pushing on them through the bearings opening with a thin screw driver. These come out easily. Next, I used a socket that matched the outside diameter of the bearings as closly as possible to drive the bearings out. After applying heat around the bearing bore with a heat gun, I gently drove the bearings out from the seal side toward the inside of the case cover.

9 This shows how I set up the bearings and spacer for insertion into the case body. I used a long 3/8" UNC bolt with a nut to press the bearings in. The bolt used should be as large in diameter as possible yet loose through the bearing bores.

10 To back up the new bearings, I used one of the old bearings and some washers.

11 The washer on the pump cavity side needs to be large enough to span the whole cavity and be smooth so no damage can occur to any of the surfaces while pressing.

12 Tighten the nut by hand only while aligning the bearings to the bore. The bearings must be in alignment for proper insertion.

13 Insure the whole assembly is centered and the washer is sitting squarely against the housing. While aligning, tighten the nut just enough that the assembly will stay centered and so you can adjust position.

14 Once there is good alignment, slowly tighten the nut to press the bearings. The bearings should fit tightly in the bore, requiring a small amount of effort to turn the nut. The feel of the tightening should be smooth and consistent through the whole pressing distance. Do not force the nut if there is binding. If there is binding, check the alignment. Loosen the assembly if necessary. If you have started to drive the bearings in crooked you must remove them and start over. If everything is properly aligned, however, the bearings will go in straight. Press the bearings in until the back bearing is flush with the back surface of the bearing bore. Do not leave any of the bearing sticking out past the casting surface.

15 Here I have the new bearings pressed in as viewed from the outside of the case cover (seal side).

16 I assembled the new shaft and impeller at this point so I could check the bearing placement. I used blue Loctite on the screw and tightened to a torque of approximately 7 foot pounds.


18 After sliding the impeller shaft fully into the bearings (until the step of the shaft bottomed on the bearing face), I used a feeler gage to determine the clearance between the aluminum housing and the back side of the impeller surface. Here, I had a little more than 0.005" clearance. If there is no clearance, press the bearings in a little more but don't go too far either. You must have clearance here, but too much could result in the impeller rubbing on the pump cover.

19 I temporarily installed the snap ring to check the space between the back side bearing and the snap ring. Ideally, the snap ring should be snug against the inner bearing race. However, a few thousandths of an inch will not pose a problem. Of course, the impeller side clearance is very important so the impeller cannot rub. Using the stock parts, there is no possible adjustment for clearances other than bearing depth. Clearance on the snap ring side indicates dimensional problems with the installed parts.

Here is my gripe about what I consider a poorly designed water pump. The bearing bore is designed such that there is no step (counter-bore) inside to hold bearing position. The only thing that prevents the bearings from moving during engine operation is the tightness of fit. In theory, this is acceptable, but in practicality, it makes the assumption the world is perfect. The truth is, conditions could arise that would allow the bearings to float one way or the other. In my case, the bearings floated out of position far enough to completely disengage the impeller shaft from the driving mechanism. I suspect the reason was bore expansion from engine heat which could cause the bearing fit to be loose. To minimize the possibility of this occurring again, I used cylindrical retaining compound on the outer bearing surfaces. Realize that cylindrical retaining compound will be of little benefit unless the bearing bore size is correct. Fortunately, the bearing fit here was tight.

20 Using calipers, I measured the height of the inner (oil side) seal.

21 A depth gage or back side of a caliper can be used to determine the available oil seal bore depth. The back side of the oil seal will butt against the outer race of the bearing. The front of the oil side seal must not protrude past the lip where the back of the front (coolant side) seal will sit. If it does, the bearings were pressed in too far. If the bearings are too far in, they must be driven back and re-pressed.

22 The seals should be pressed in same manner as the bearings, but from the other side of the case cover. Here, I used the old pump bearings along with some washers to backup the seal when pressing.

23 Alignment is crucial. Tighten the nut slowly until the seal bottoms against the bearing surface.

24 When the oil side seal is properly located, the bore for the outer seal will be completely visible. Notice the open (cupped) side of the seal is facing inward, toward the oil side of the engine.

25 The outer seal should be pressed in the same way as the inner seal. It should be pressed in until it bottoms against the counter bore. The open side of this seal should face outward.

26 Finally, the impeller-shaft assembly can be installed. Don't forget to install the snap ring on the back side.

Prepare to install case cover.

  • Make sure all parts are clean.
  • Gasket surfaces must be clean and free from damage.
  • For dimensional reasons, use only the stock case cover gasket.
  • Inspect other seals and components, repairing as needed.

27 Insert the shaft into the oil pump gear as shown here. Make certain the gear teeth are properly engaged. Next, place the cover gasket on the engine side because the dowels there will hold it in place. Now, you can slide the case cover on. This can be a pain so be patient. While you position the case cover, you must keep it positioned squarely to the engine while also being aligned to the kick start shaft and the oil pump gear shaft. Do not attempt to force the case cover on, but rather try to accurately wiggle it on with finesse. If you get it in a bind, pull it off and start over. Once the case cover is started correctly, you must also pay attention to engagement of the water pump driver. While positioning the cover, continually check rotation of the water pump to feel for engagement. When the pump shaft is correctly aligned, the case cover should go on easily. Very light tapping with a soft hammer is ok, but again, focus on accuracy and finesse, NOT force.

28 Before tightening the case cover bolts, first install the upper oil filter housing screw temporarily. This is so the screw hole will be properly aligned when all of the other bolts are tightened. You should wait to install the oil filter until after the case cover is properly installed. I recommend using a drop of blue Loctite on all of the screw threads. Finally, insure the water pump cover is in good condition and install. That's it! Don't forget the fluids and check for leaks before you go riding.


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