K Bike Water/Oil Pump Rebuild Using New-Style Seals

By Don Forsman
Original Article May 2003

[Due to a design change in the seal for the water pump, it was time to revise a portion of the original rebuild tech procedure. Thanks to Don Forsman, IBMWR now has pictures and a step-by-step procedure to install this new part. Thanks Don! - Jon Diaz]

This article is considered an addendum to the original tech procedure, and assumes that you have already begun the reassembly process, and have installed your oil seal. Here is a picture of the oil and water seals.

new seal

Photo courtesy of Clif Lines

You can think of the water seal as consisting of two parts: the inner part and the outer part. The outer part is that part that is pressed into the water pump housing and remains stationary when the engine is running. The inner part is the part that turns with the shaft and impeller. You will be putting the outer part into the housing and then putting the shaft through the inner part from the back or oil side. This must be done carefully or you will be buying more than one seal to get this job done.

Now, you will need a "special tool" to press the water seal into the housing. I used a piece of PVC pipe which I chamfered on the inside to just fit over the seal and bear on the seal lip.

new seal

new seal

Make sure the pipe you use has a large enough inside diameter to pass over the inner part of the seal and not put any force on it. The blue "goo" on the outer part is the sealant. There is more blue goo on the inside of the inner part that you are going to have to deal with shortly. I then drove it home using a rubber mallet on the end of the PVC.

Here is the installed water seal.

new seal

Now that you have the outer part of the seal properly seated in the housing, take the shaft with the gear on the back side and *carefully* insert it from the back or oil side of the housing, through the oil seal you just installed and then up through the inner part of the water seal ONLY UNTIL IT REACHES THE BLUE GOO. Then STOP!!! If you keep pushing you will destroy the seal.

Now, take the bolt that held the impellor to the shaft. Get some washers that will fit it. You are going to take that bolt and washers and use it to pull the shaft up through the blue goo in the inner part of the seal. (the next pic shows the bolt, washer, and shaft end right at the inner blue goo) The washers will be pushing on the surface of the inner part of the seal so it cannot be forced out by the shaft as it comes up through it. You may have to hold on to the gear on the back side of the shaft as you tighten the bolt to keep things from turning. I think I used a small piece of hardwood to jam it. (JD: the oil pump side of the shaft should have an opening for an allen wrench, although juggling all of it is a three-handed job.)

new seal

When you get the shaft to the front of the inner seal, stop and remove the bolt and washer. Now take the spacer that came with the new impellor and use it instead of the washer to draw the shaft through that last little bit. The spacer is recessed and the shaft should go into it.

Check the back side where the gear is. Is the gear against the housing or is it standing out a little? You might wish to continue pulling the shaft just a little bit more, using another washer, to get rid of that extra space. I did that and found that the impellor spacer on the front was no longer in contact with the inner part of the seal. But, the spacer does not act as a seal (the blue goo does) and it, the shaft, and the impellor are all spinning together. And, the space was only the thickness of the washer. I only worried about it until I went out riding. It hasn't leaked yet.

I put the spacer and impellor back on and bolted it back down using blue loc-tite on the bolt.

new seal

One other thing I did was replace two of the long bolts with stainless ones. Those were the long bolts that hold the housing to the engine block, not the shorter ones that hold the outer cover to the housing. The long bolts I took out were so badly corroded that the hex socket ends were enlarged and required an SAE allen wrench to remove them.

Now you may follow the rest of the previous tech article for completion of the reinstallation process.