Getting into the guts of the CRF450 Flat Tracker.

A couple of months ago I detailed my experience with Moto Anatomy and getting trained by none other than Johnny Lewis, AFT racer #10. It was a great weekend and I learned a lot from having someone give me immediate feedback on my riding form and ways to get faster around the dirt oval. While there, Johnny noticed that I was weeping a bit of fluid. I did my research and found put that it was time to rebuild my CRF450's water pump. This post shows you the extent of what a job like this takes so maybe you could tackle something like this for yourself.

The tell tale signs of a leaking water pump seal. Honda uses a common drive shaft from the crank to turn the water pump impeller. This leaves the engineers with the problem of keeping the oil for the crankcase and the cooling system fluid separate. There are two seals along the shaft, an oil seal and a water seal. In the space between them, the Honda designers left a small hole in the bottom of the cover. If oil is leaking out, the oil seal is bad. Same idea for the water seal. When you replace one, you have to replace the other. The impeller shaft and the shaft bearing are also considered consumable items. Thankfully Honda made the whole process easy to do on a Saturday with just the most basic tools. The parts were also pretty reasonably priced as well.

More evidence that I was sitting on a potential engine blowing time bomb. The top of my under slung muffler was coated in a thick layer of mud from the track and the water leaking from the seep hole in the engine case cover. I also checked the radiator water level to find that it looked much emptier than it should be. I filled it with some tap water temporarily to see how much water it lost. It took an uncomfortable amount of water to be able to see the water level in the radiator. In another post, I added the Motion Pro coolant overflow bottle as well as a higher pressure radiator cap to the CRF's cooling system. That was in response to the bike getting covered in mud from coolant dripping out of my radiator overflow tubes. I believe that maybe the seal was starting to go and that by putting on the higher pressure radiator cap, I may have increased the pressure enough to finally take the seal over the edge.

I have been putting off this work for a couple of months. This pile of parts amounts to $150.00 of work spent working on spreadsheets and attending group phone meetings. Not a huge sum by any means, but October and November saw the race budget take a back seat to the normal family issues. Fixing Mrs. My Motorbike Obsessions vehicle and a credit card that was still warm from the June trip to Tokyo meant that this work had to wait for a bit. The good thing about this delay was that I spent some time searching for a bargain. CRF's Only came through and I was able to find a complete kit to rebuild the water pump in one place. I also picked up some miscellaneous brake line guides that were missing from the bike being built into a flat tracker.

The first part of the work involved draining all the vital fluids. Usually this is where the work starts to go bad. This time I only had a couple of drops of coolant to clean up after I was done. I got the water pump impeller pulled off after putting the bike in gear and dropping the rear tire off the Pit Bull stand. So far so good. One of the great things about this bike, and most Japanese brand bikes in general, is that I can disassemble almost the entire motorcycle with an 8, 10 and 12mm socket set. Once The fluids were taken care I pulled the brake pedal and kick start lever. In order to get the kick start lever off, I had to break out the heat gun and warm it up. A little persuasion with a pry bar got it off and out of the way. Following that, I pulled off the right side engine case whereupon all of the remaining transmission oil made its way onto the floor of the shop. A quick cleanup and I was ready to begin the rebuild of the water pump system.

Except for the water pump seal, the water pump shaft, oil seal and bearing came right out. The water pump seal required me to use the heat gun again. Thankfully the aluminum of the right side engine cover heated up quickly and the seal exited its former home. I did gouge a small part of the seal boss, but nothing a little file and sandpaper work couldn't fix. The top water pump shaft showed a little sign of wear, but nothing that would have prevented me from using it again if I had to. Since the kit I got from CRF's Only was only $100 and came with every part needed to replace the whole system, I replaced it with the new one in the bottom of the picture above. The inside of the transmission area was clean and free of any worrying debris like chunks of clutch or gear teeth. The clutch basket looks like it may be an aftermarket unit. Entirely possible since this was at one time a built engine. The only part changed when I bought it was the cam that got replaced with a stock unit to tame some of the power.

Changing out the water pump parts was a simple remove and replace repair. I cleaned up all of the old gasket material and made sure it was ready to go back on. Just like the service manual says, "installation is the reverse of the removal". The distorted o-ring in the picture on the right was the new one for the water pump housing. It is a shaped o-ring and my new one wasn't the right shape. I'm not sure if it was made incorrectly or if it got messed up in the packaging, but I couldn't get it to stay long enough for me to bolt the housing back together. I cleaned and reused the old one. We'll see how it lasts. After everything was bolted and torqued to spec, I refilled the transmission oil from the remaining quart leftover from my last oil change. I also used the last of my Redline Water Wetter from changing out my coolant in the FZ, and needed to get another bottle before I was able to run the bike for testing. I'm got a good test ride in my cul-de-sac to make sure nothing was leaking once the bike got up to temperature. All was good to go!

Well, thats it for this post. The winter holidays are coming an I plan on getting out and getting some riding in. I will have a couple of weeks off and I plan on going to do some flat track and maybe some supermoto. I also want to see about some trail riding as the deserts of SoCal are really nice this time of year. Hang in there for a ride report on how the new supermoto wheels and tires work out as well as what ever other motorbike adventures I can get into. Take care and ride safe friends!

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