LC4 Water Pump Rebuild

By: AdvWisdom
Title: LC4 Water Pump Rebuild
Sourced From:
Published Date: Mon, 20 Jul 2020 01:01:41 +0000
Rebuilding the LC4 Mechanical Water Pump

If your water pump is leaking coolant into your engine, it�s time to replace your water pump seal and bearings right away. Coolant is corrosive to various internal parts of an engine, so it is best to address the problem as early as possible.

How does one know if coolant is getting into one�s engine you ask? Symptoms of coolant getting into the engine include evidence of milky or opaque looking oil and quite possibly a noticeable loss of coolant in your radiator. LC4 mechanical water pumps are notorious for seal failures, so this is the first place you should look in searching for the source of your problem if you observe milky oil in your engine.

One caveat… it is possible under very rare circumstances that condensation can cause your oil to look a bit milky. This could occur under unusual riding practices that prevent your engine from fully warming up, such as: Ride 2 miles, stop. Time elapses, start the bike and ride another 2 miles. Let the bike sit for two days. Repeat. It would also be more likely to occur in cool, damp environments than in desert conditions.

In my case, I had no evidence of coolant getting into my engine, but I chose to rebuild the water pump partially for preventative maintenance (since I already had the rocker cover off for another procedure), but mainly because I wanted to learn how the pump works.

Rebuilding the water pump is not particularly difficult, but it does require some basic tools, and some mechanical aptitude. If you are the kind of guy that can (or has) swapped out your main bearing in your pre �03 LC4 engine, then this won�t be difficult at all. The parts for rebuilding the water pump totaled $47.37, whereas purchasing a new water pump costs around $165.00. It took me about 2 hours to do.

The KTM Factory Manual is fairly simplistic regarding this procedure, and they devoted a total of nine sentences, one diagram and one photograph to the task. It is my hope that this technical article will be a more thorough and clear document that may aid and guide others contemplating doing this procedure.

I recommend that you read this entire article before beginning the procedure. This will give you an overview of the steps involved, and will afford you an opportunity to assess your skills and decide whether or not you are prepared to tackle this procedure.

First off, this is the list of parts I procured. This includes all of the major components to rebuild your water pump. The only items I didn�t replace were the water pump housing and cover (and the 4 associated case screws), the water pump shaft and the rotor screw. You may decide to forego some of the items I�ve listed below, but until you have the water pump disassembled, you won�t know what shape it�s all in and what you�ll need. Since I wanted to get back on the road ASAP and with peace of mind, I decided to do a complete rebuild. Here�s the list of the parts I bought:

There’s something I would like to mention about parts prices. If you wrench on your bike quite a bit, you are probably buying parts on a regular basis. There are ways to get discounts that can really add up. For example, I get a 25% discount on KTM parts, so I paid $47.37 for the above list of parts instead of $63.12. It�s worth shopping around to get a break. If you don�t know where to start, ask a known wrench monkey from the asylum about the ins and outs of discounts.

Here is a list of recommended tools and supplies. Some are absolutely required, and some will just make the job easier. I used every one of the following to rebuild my water pump.

1 bottle or tube of Loctite 648 Retaining Compound

This product is not so easy to find. You�re unlikely to find it at a local hardware or auto supply store. You might find it at a local machine supply shop, but I wouldn�t count on it. An on-line eVendor is probably your best bet. A quick Google search came up with this:

I have no affiliation with the above business, nor am I recommending that you necessarily purchase from them. I am merely giving an example of one possible source for this product.

1 bottle or tube of Loctite 243 (the readily found blue medium strength Loctite)

A pair of straight snap ring Pliers (ideally one that can convert to do both directions � squeeze and stretch). You can find these at a Sears or many Auto Supply stores.

A torque wrench: Ideally a 1/4� drive low value one (in/lbs). These are not inexpensive, but if you�re going to be wrenching on your bike, they are a great investment to make. I bought mine (a snap-on) on Ebay for $75.00. It even came with a recent calibration certificate.
4mm Allen key
5mm Allen key
6mm socket
9mm socket (3/8� drive)
16mm socket (3/8� drive)
17mm socket (3/8� drive)
1/2″ deep socket(3/8″ drive)
5/8� deep socket (3/8� drive)
15/16″ socket
3/8� to 1/2� drive adapter
Rubber mallet
Gasket Scraper
Razor blade
Orange wood sticks
(ask your girlfriend, wife or manicurist about these)
A couple of scrap pieces of wood

In order to remove the water pump, you will first need to remove the rocker cover. If you haven�t already read Creeper�s excellent guide on how to do that, you should click here. Creeper’s Guide to Re-sealing the LC4 Rocker Cover

Step 1
Before you actually do remove the rocker cover however, I recommend that you remove the top two hoses labeled #1 & #2 (of 4 total) in the photograph below. The 6mm socket will take care of the bigger hose, and a pair of pliers will handle the spring clip on the smaller hose.

Incidentally, you can remove the hoses after you have the rocker cover off, but then you�ll have to be more careful in order to prevent accidentally spilling any coolant into the open rocker box.

If you�re like I am, you don�t like doing any extra, unnecessary work. With that in mind, you won�t need to remove the lower two hoses (labeled #3 & #4 in the photograph below) from the water pump cover in order to remove the water pump, but feel free to remove them if you feel more comfortable doing so.

Step 2
Be careful to pull the hoses from the water pump cover slowly, and have a bucket below to catch the coolant that will drain. I started by removing hose #2 from the water pump housing, and I held a funnel underneath the end of the hose to direct the coolant into a bucket waiting below as I slowly pulled the hose off. Some coolant will drain from the hose, and some will gush out of the pump housing. Just let it drain out for a minute before going on to hose #1.

Sake (the MotoKitty) says please make sure to mop up any spilled coolant and dispose of the used coolant in a safe manner to prevent accidental poisoning any kitties, doggies or other curious critters ; )

Step 3
Since you diligently read and followed Creeper�s instructions , your engine is at or close to TDC-C, and therefore the slot (or groove as KTM refers to it) in the camshaft driving screw should be aligned vertically or nearly so. You should, therefore, be able to lift the water pump up and out of the engine case without difficulty. You should not have to force anything. When the slot is properly aligned, the water pump should just lift out. To see the slotted (or grooved) driving screw, scroll down a bit to the next photograph.

Step 4
Okay, now you should have the pump extracted from the engine case, and dangling by the two rather stiff radiator hoses. Remove the four 5mm Allen Head bolts from the cover, and gently pull the water pump cover off of the water pump housing.

Step 5
Now�s a good time to clean off the old gasket from the mating surfaces of the water pump housing and cover. You can use a gasket scraper, a razor blade, and some acetone to clean the surfaces of the old gasket material. Try not to scratch any of the metal surfaces. Now you can leave the water pump cover to dangle like so until you�ve rebuilt the water pump:

Here�s the Water Pump housing removed and ready to be rebuilt:

Other than a little gunk on the rotor, mine didn�t look to be in too bad shape, but the cover gasket was completely shot, and I�m surprised that my cover hadn�t been weeping coolant already.

Step 1
Remove the 4mm Allen Head bolt and washer from the rotor (impeller) side of the housing. I used a crescent wrench on the engine side of the pump shaft to keep the shaft from spinning while you unscrew the bolt. Clean the rotor screw of the residual Loctite gunk that you�ll find on the threads.

Step 2
Pull the rotor straight off of the shaft. You may need to judiciously use a pair of pliers as I did. It didn�t take much force to pull it off, so you should be able to get it off without mangling it if you are intending to reuse it during in the course of the rebuild.

Step 3
Next, you want to use that pair of snap ring pliers, and remove the two circlips from the camshaft side of the housing. Please refer to the photograph above. The inner small circlip requires the snap ring pliers to be setup for spreading force, and the outer large circlip requires squeezing force.

Now, unless you have access to a hydraulic press, here�s where you have to get a little creative. I actually could have gone to MotoMike�s shop to use his press, but I didn�t want to take the easy way out. I wanted to do the whole job with the kind of simple hand tools that most of us probably already have. So here�s where the scrap wood, comes in handy:

Step 4

I straddled the pump housing over two pieces of scrap wood that I setup on top of a third piece. I found that a 9mm socket along with a 3/8� to 1/2� adapter would be the perfect size tool to press the water pump shaft out of the housing and seal.

You want to make sure that you press the shaft out towards the camshaft side of the housing, NOT towards the pump cover side. A couple of good taps with the rubber mallet should persuade the shaft and associated bearings to exit the housing.


Step 5
Now take a 16mm socket, and using the rubber �persuader,� tap out the old seal:

Step 6
Now, clean up that water pump housing. I used a combination of brake/carb cleaner, acetone, paper towels, Q-tips, and orangewood sticks. Orangewood sticks are the wooden sticks used on cuticles during a manicure. They are great tools for working on metal surfaces. They won�t scratch the metal, and they can scrape off all kinds of junk rather well. You can shape the edge of one with a knife to get into tight spots. Using orangewood sticks is a trick I learned in my assistant camera days. We would use them to clean film emulsion gunk off of the delicate movements and gates of motion picture cameras.

Step 7
The final step in the disassembly process is to remove the two grooved bearings off of the water pump shaft. I found a 5/8� deep socket fit over the shaft and onto the inner bearing race pretty well.

After a few more taps with the �persuader� the bearings will begin to migrate off of the shaft. I then turned the shaft/bearing assembly over, and supported the bearings with the 5/8� socket while tapping the shaft out the rest of the way with a 9mm socket and the 3/8� to 1/2� drive adapter. Sorry, I didn�t take any photographs of that last step.

Here�s a great idea I got from MotoMike: put the water pump shaft in your freezer for an hour or so before you press the new bearings onto it.

The KTM Factory Engine manual instructions say to �Cover new shaft seal ring with Loctite 648 and press in with printing facing outward.�

The first thing I wondered is which way is �outward?� I assume they mean that the side of the new seal with printing on it should face you as you press the seal into the housing. I have to say that as far as I could tell, the seal looked symmetrical, and appeared to be identical on both sides. There was, however, some pretty minimal and tiny �printing� on one side of the seal only.

Step 1
I covered the outer circumference of the seal with a bead of the Loctite 648, and pressed it in with a 17mm socket and the �persuader.� I had to give the seal a few good whacks to get it to seat evenly and flush with the flange that it rests against in the housing. The seal seems fairly durable, but be careful of the delicate �lips.� Mine doesn�t look any worse for the wear after being �persuaded� to seat in the housing.

Here�s� the new seal installed:

Here�s a less than clear piece of instruction quoted from the English version of the KTM Factory Engine Manual:

�Properly lubricate new grooved bearings, and press in to stop with the open sides facing each to them.�

I have a few �issues� with that line of instruction. First of all, the bearings specified are sealed bearings, with identical sides. There are no �open� sides at all. So there�s no lubricating to be done, and no particular orientation to adhere to during installation. Perhaps the original bearings have been superseded at some point as Creeper has suggested might be the case. All I know is that the bearings I removed from my �02 640 Adventure�s water pump were exactly the same type of sealed bearings as the new ones.

Step 2
Okay, so now you can retrieve the water pump shaft from your freezer, and put a light coating of oil on the shaft. I placed the first new bearing on a flat piece of scrap wood, and started inserting the shaft down into it. The idea is that the flat scrap piece of wood will support both the outer and the inner races of the bearing as you press the shaft down into the bearing. I used the rubber mallet �persuader� to drive the shaft down until it was flush with the bottom of the bearing � please refer to the first photograph below.

Step 3
Now put the second bearing down on the wood, and place the shaft + first bearing assembly on top of it. A tap or two, and the shaft should sit flush with the bottom of the second bearing� as in the second photograph below, but wait� we�re not done yet.

Step 4
I found that a 1/2� deep socket that fit over the shaft well, and contacted only the inner race of the bearing. The socket can therefore be used to support the bearing (on the inner race) in order to drive the shaft down to seat the bearings. I placed the shaft/bearings assembly onto it.

To put it another way, the idea is that the socket�s edge will only make contact with the inner race of the second bearing you have fitted onto the shaft � please refer to the two photographs below. A few taps with the �persuader,� and the bearings should now be flush with the flange that will mate with the seal once installed in the pump housing.

Here�s what the bearings will look like when they are properly seated on the shaft:

Step 5
Now install the small circlip (part #2 on the diagram at the top of this guide) to retain the bearings on the pump shaft:

Step 6
At this point I put the pump shaft/bearing assembly in the freezer for a couple of hours hoping that it would help ease the installation into the pump housing. I do think it helped. When it�s good and cold, take the assembly out of the freezer, and coat the circumference of the bearings and the shaft with a little oil. You should also lubricate the lips of the seal before you insert the shaft.

Before beginning the insertion process, make sure that the spring rings that rest under the seal lips on both sides of the seal are securely in place.

Step 7
Place the pump body on a flat piece of scrap wood, and use a 15/16� socket with a rubber mallet to drive the shaft/bearing assembly in to the pump housing. The idea here is that the 15/16� socket will make contact with the outer race of the bearing only.

I found this step to be a bit tricky. Take your time, and make sure you drive the assembly in straight. It will take a little force to drive it all the way in, but you want to make sure the assembly is going in straight and not cocked. If it starts to go in cocked, try to tap on the high side to straighten it out before it gets too angled. You may have to back the whole assembly out and start over if you can�t correct the angle of entry to be true and straight.

You may need to stop and look at the underside to see how the shaft is mating with the seal periodically. I found the seal had a tendency to fold the lip over on itself causing a poor seal against the shaft. I had to back the shaft out several times before I finally was able to seat it properly at the critical stage of penetration with the aid of a flathead jeweler�s screwdriver. I used the screwdriver to carefully make sure the seal didn�t fold over itself as the shaft pushed through. Be careful not to damage or puncture the delicate rubber seal with the sharp edges of the screwdriver.

Ultimately you are hoping to get the seal to look like this when properly seated:

Step 8
Now use the snap ring pliers (in squeeze force mode) to install the large snap ring to retain the shaft/bearing assembly in the housing:

You�re almost done!

Step 9
Reinstall your old rotor after you�ve cleaned it up, or install a new one if you bought one, and use a new washer for the rotor screw. Use some Loctite 243 on the threads of the rotor screw. You will need to use the crescent wrench again to hold the shaft steady from the other side as you tighten the 4mm Allen Head screw.

Step 10
Next, install the two rubber O-rings. It will be obvious when you are installing them, but the thicker one goes in the wider groove, and thinner one goes in the narrower groove:

Step 11
If you haven�t already done so, clean off both the mating surfaces of he pump housing and the pump cover, and make sure they are oil free and dry. I used a combination of brake/carb cleaner and some paper towels. Hold the gasket in place with the four 5mm Allen Head screws, and screw the cover onto the pump housing as follows: First screw the 4 screws in finger tight, then torque them to 10Nm (7.38 ft/lbs or 88 inch/lbs) in a diagonal pattern, like this for example:

1 3
4 2

Step 12
Clean the machined cradle (where the water pump housing mates with the seam of the rocker cover and head case) of any oil or residual gasket material � refer to photograph below. Align the pump shaft�s key with the slot or �groove� in the driving screw, and carefully slide the pump down into the machined cradle in the engine case.

Congratulations� you�re done! Now just seal and install your rocker cover as per Creeper�s guide, and check your valve lash, and that�s it, other than adding some coolant to make up for the coolant you drained for the procedure. You might want to lean the bike way over on the left side to try to get some coolant to find its way to the water pump to prime it. Be careful, and have a friend help you if you can.

That wasn’t so hard was it? Go ahead and grab yourself a beer. You earned it.

I would like to thank Creeper for his great work on all of the technical guides he has written for the benefit of all LC4 owners, and also for proof reading my first attempt at writing a technical article. I know I can�t approach Creeper�s precision and concise explanatory style, but at least I know from his example of excellence what I�m striving for.

I would also like to thank MotoMike for his great suggestion regarding putting the shaft in the freezer prior to installing the bearings, and for lending me his pair of snap ring pliers and a bottle of Loctite 648.