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MTF Canadian Contributor
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This article will explain the rebuild and repair procedure for the above described Kawasaki Jet ski engine resulting from the number two (2) piston’s skirt collapsing caused by a blocked water intake hose. The engine rebuilding principals covered in this article can and should be applied to all engines regardless of the make.


Refer to your service manual for complete and explicit instructions regarding this and all topics regarding your watercraft. This is a guide which may not address every aspect of your particular situation and or watercraft in general.


My brother owns this particular Jet Ski which is manufactured by Kawasaki®. He had purchased the watercraft and rode problem free for most of the season in the first year he bought it. While at his camp (Trailer park) he had rode the Jet Ski one afternoon and inadvertently left it parked on the beach. (This allowed the waves to push beach sand up into the rear of the hull which was later determined to be the cause of a blocked water intake inlet) It wasn’t until the next day that he decided to ride again.

He started the ski in the usual manner and headed out on the lake for a morning run when without warning (as explained by him) the engine malfunctioned and lost power. He was able to limp the ski back to the shore-line and had the engine off rather quickly after that.

He decided to remove the engine and bring it to my place as I live not far from his camp and proceeded to disassemble the top end of the engine in an attempt to ascertain the cause and extent of damage if any. I supervised the disassembly at that time. [FIG A]

View attachment 632146


He removed the spark plugs and heads from all three (3) cylinders and quickly noticed extensive damage to the number two (2) piston and head. He further removed all three cylinders which ultimately exposed further damage to the number two (2) rod, cylinder walls and rod bearing.[FIG 1]

[FIG 1]
View attachment 624722
Inverting the engine showed catastrophic damage to the lower crankcase which had a rather large hole below number two (2) piston.


Upon a closer examination of the engine, I determined that the extent of damage consisted of the following;

The piston skirt had collapsed due to over heating. (later determined by me to be a blocked water pickup line at the rear of the water craft which was caused by the pounding of waves while the craft was resting on the beach) A portion of the skirt had broken away from the piston and had become lodged between the piston and cylinder wall which resulted in scoring the walls of the cylinder and piston.

A portion of the piston skirt had also fallen into and below the crankshaft (crank) area and was swept below the big end of the connecting rod and forced through the lower crank case by the rotation of the crank. The above also bent the connecting rod into what appeared to be an ‘S’ shape.

A closer examination of the crank revealed an over heating of the connecting rod bearing and journal. In short; this engine was good for use as an anchor but that was about it at this point.


I advised my bother that a need for a new crank, piston and rod along with a lower case and or perhaps a replacement engine was in order. He packaged up the engine (put all the pieces in a box/s) and headed home.


After a search of the internet of available used engines and the costs associated with such ($2,000.00 with shipping) he quickly determined a search of EBay® may be more cost effective however; used cranks were expensive and would require reconditioning regardless. Further; cranks and engine cases were quite scarce.

He also learned that this type of engine failure was quite common and likely the reason for the shortage of cranks and cases being sold today.

Reconditioned/rebuilt cranks were found to be available however; cost was about the same for the entire engine.


A year had elapsed since my bother had towed his ski over to my place after the engine melt-down and it had become nothing more than a planter. The wife was annoyed with its presence and frankly; so was I as it had been a pain when cutting the lawn; having to use the whipper-snipper to cut the grass under the trailer and always having to watch I didn’t scrape the side of my lawn tractor cutting close to it.

I decided to repair (and cover all associated costs) the engine as a gift and so began the task of rebuilding the engine. I had my brother box the engine parts and deliver them to my home. (I had the hull but not the engine on my property)


Licenced as an automotive technician in both cars and heavy trucks, I felt I could manage rebuilding this engine as the principles of all engines are generally the same and so jumped in with both feet.


The first order of business was to see if I could find someone to weld the lower case as this was the deciding factor as to whether or not this build could take place. If the metal was anything other than aluminum or magnesium, I would have welded it myself being an accomplished welder however; I simply do not have any experience with this type of welding and so in this case, I decided to leave it to the pros. The lower case was welded by a friend of mine (John) at a local machine shop at a cost of $150.00

Note: If doing this procedure yourself; make sure the lower half of the case is mounted to a steel bench and clamped tightly in place as the welding will tend to warp the case especially if welding occurs in the middle. Also ensure it has cooled considerably before releasing from the table/bench.

Some warping will inevitably occur and can not be helped however; if not considerable, the torque procedure will straighten it out. Once welded and cooled, check to see that the hole is completely welded by spraying Brake Clean® in the cavity and look for leaks. Don’t use water because the leak may not show up. You need to use a liquid with properties similar to gasoline to ensure it will not leak and by all means; do not use gasoline as it is much too dangerous.

Shown below is the finished welding job of the lower crank case. Note the bead of weld at the middle of the case. [FIG 2]

[FIG 2]
View attachment 624730

In the picture below, you can see that after having sent the crankshaft to the machine shop, the following work was completed; [FIG 3 & 4]

All three (3) connecting rods and lower bearings have been replaced; (red arrows) both crank bearings to the left and right of the number two (2) connecting rod have been replaced; (blue arrows) and both crank journals to the left and right of the middle connecting rod (yellow arrows) have been replaced.

You may be asking why I chose to replace all three connecting rods and lower bearings as opposed to just the middle one and the reason is because the cost to replace them when the crank was being repaired vs replacing the upper rod bearings and or pins was comparable.

Why would you have to replace the bearings you ask?

It turns out my bother failed to see the importance of keeping the pistons, pins and bearings with the same cylinders they came out of during the disassembly process. Is that important you ask? - Very.

The wristpin bearings will leave a wear pattern on the connecting rod upper ends and piston pins over time. If you do not remember to keep the pistons in the cylinders the came from, you may put the wrong piston bearing and pin from one cylinder in another.

The conflicting wear patterns may take the engine apart as a result not to mention the fact that each piston must go back in the same cylinder as well because of the ring end gap measurement. Each may differ from the other.

The crank bearings were replaced because I felt that there was uncertainty as to the condition of both bearings in this area given the nature of the failure.

It was unclear to me whether or not scoring had taken place on the crank journal pin and or bearing and the reason I felt it necessary to replace them. Peace of mind in this case cost $60.00

The crank was then balanced and shipped back to me.

Cost of Crankshaft repair; $575.00

Note: this crankshaft had the connecting rod journal damaged because of overheating the piston which caused the skirt to fail and place debris in the bearing which resulted in damage to the crank journal. You can not simply press out the journal pin from the journal chops as this crank is pressed together in sections. One journal is constructed with the pin and one is not. (Two (2) pieces; not three (3) ). If a crank pin needs to be replaced as in this case; the chops need replacing as well.

[FIG 3]
View attachment 624738
[FIG 4]
View attachment 624746

Shown below is the scoring that occurred when the piston skirt wedged between the cylinder wall and piston. These have to be removed as a new piston and ring set will be installed. [FIG 5]

Figure 6 shows a ridge that will need to be removed as well.

Note: A failure to remove this ridge will likely result in breaking the top compression ring on the upward stroke.

[FIG 5]
View attachment 624754
[FIG 6]
View attachment 624762

To repair the cylinder, I will need to hone it. Take your time here; you want a professional job with an end resulting in a clean bore, no ridge and a beautiful 45 degree crosshatch stone pattern left on the cylinder wall.

I am using a brand new hone with medium course stone. Honing is completed using long stroke low RPM (revolutions per minuet) rotations.

The strokes must be rather quick to produce the correct crosshatch. Short, slow strokes with high RPM will produce more of a circular pattern like a tight cork screw and you do not want this. [FIG 7]

Strive for a finished pattern as shown in figure 8.

Note: The cylinders I am honing are plated with Nikasil®. This is a very hard material which dissipates heat very well. If your cylinder has extensive damage; you may need to have it professionally re-plated.

[FIG 7]
View attachment 624770
[FIG 8]
View attachment 624778

In my case, I chose to address each mating surface with a variable speed orbital sander with a 220 grit paper as some of the surfaces were troublesome and removing the gaskets and sealants proved difficult.

A very low RPM and no hand pressure with frequent changes to the paper proved to work well however; do not get carried away during this procedure as you can easily destroy your engine if you sand too much or use any pressure other than the weight of the sander.

Remember, most parts on this engine are aluminum and not forgiving when sanded. The sander must be 90 degrees to the mating surface. Steel surfaces may be more forgiving although care must be exercised regardless. Better still; if unsure or reluctant, do it by hand using a gasket scraper.

Figure nine below depicts the three cylinders and heads honed, cleaned and degreased.

[FIG 9]
View attachment 624786
At this point, you may wish to grab a beer, a bite to eat or both. I started at 10:00 this morning and will go to the wee hours of the morning.

View attachment 625106

I cannot emphasize the importance of cleanliness enough when dealing in engine rebuilding. You can never have an engine too clean however; can have one not clean enough.

With respect to threaded areas; ensure each and every threaded area has been chased using the proper tools. Threads that have not been chased or nuts, bolts and studs not having been cleaned can produce improper torque readings and or possibly result in a leak.

Chasing means to run a tap or die in or over a threaded area. Ensure the chasing is done using a lubricant and in this case I am using WD-40®. Be careful not to cross-thread any hole. Nice and easy and right to the bottom of the bore. [FIG 10]

Continually spray your lubricant in the hole especially if it is aluminum but on anything regardless. When you think you have done a good job; blow it out with the air hose, lubricate and one final run should do it. All holes should be very clean and debris free. Use a wire wheel to clean the threads of any bolt or stud as well.

Wash the parts in soap and water whether aluminum or steel and blow dry with an air hose and as a final step; I use Brake Clean® on the threaded holes, blow dry with an air hose and very lightly lubricate with WD-40®

Note: if the part is steel, ensure you apply a light film of WD-40® to prevent immediate rusting of the bare metal. I also do this with aluminum however; not imperative.

[FIG 10]
View attachment 624794

Shown below; I am installing cylinder head studs. I am doing this by placing two (2) nuts back to back which have been tightened against one another. This allows me the ability to screw in the stud with an acceptable level of pressure and ensure proper seating. [FIG 11 & 12]

Also note the use of blue LocTight® (red arrow). This particular colour (blue) is considered non permanent. Red would be considered permanent. Always check and follow the directions in your service manual for the type of sealant and procedure to be used.

Figure 12 shows all studs installed in the cylinder.

[FIG 11]
View attachment 624802
[FIG 12]
View attachment 624810

As I am installing a brand new Wisco® piston, I will need to set the ring end gap. This is very important because as the ring heats up, it expands. If it does not have the room to expand, it will damage the engine. Follow the piston manufacture’s installation and end gap procedure and settings. [FIG 13 & 14]

In my case, this piston requires a minimum of four thousands of an inch (.004) for every inch of bore. That means twelve thousands of an inch (.012) end gap.

Further in my case; because of the honing procedure, I was over this amount but within the service limit of the manual and did not require any filing of the rings.

[FIG 13]
View attachment 624818
[FIG 14]
View attachment 624826

Depending on whether or not you have large amounts of any sealant around the bolting locations, you may need to clean these areas.

Shown below in figure 15, you can see that mine will need to be cleaned. (red arrow)

Clearly; the LocTight® shown here was from the previous build indicating this engine has been apart at least once before hand.

Figure 16 shows me using a reamer to cut this debris out of the hole area. Be sure not to get too carried away with the reamer. Just clean up the area in question as shown in figure 17 & 18.

Finally; figure 19 shows the cleaned lower case ready for assembly.

[FIG 15]
View attachment 624834
[FIG 16]
View attachment 624842
[FIG 17]
View attachment 624850
[FIG 18]
View attachment 624858
[FIG 19]
View attachment 624866

In figure 20 through 23, you can see that there was some flashing of sorts produced by the connecting rod swiping parts of the piston across the face of the upper case.

This material must be removed prior to assembly because a failure to do so may result in small pieces of this debris falling away from the casting and ending up in the crank and or rod bearings.

I have chosen to use a carbide cutting bit on a variable speed drill to perform this task. Figure 23 shows the final product.

[FIG 20]
View attachment 624874
[FIG 21]
View attachment 624882
[FIG 22]
View attachment 624890
[FIG 23]
View attachment 624898

All righty then; with all the prep work completed, we can now get into the build portion of this article.

You will want to construct some sort of engine stand to complete your build on so perhaps do something as I have shown below.

Using ¾” plywood, make two ‘T’s and drill two holes in the leading edge of the wood. This will provide a place for the cylinder head bolts to slip into and make a sturdy platform for the shifting, sliding and turning of the engine as you work your way through the build.

This picture shows the rear of the engine and the side of the crank that receives the driven coupler to propel the watercraft. [FIG 24]

With the oil seals installed on the crankshaft ahead of time, lay the complete crankshaft in the proper location in the top crank case half. (the top case is upside down in this picture)

Ensure the oil seals line up in there respective grooves.

Ensure the indexing pins on all crank bearings and couplers are in their respective grooves.


Align the timing marks between the front balancer and crank gear. [FIG 25] The tooth with the timing mark must align with the corresponding mark between two teeth on the other gear.

Pour the proper amount of 2 cycle oil in the cavity marked with a blue arrow.
(Where the balancer gear sits) 1.2 ounces in this case

[FIG 24]
View attachment 624906
[FIG 25]
View attachment 624914
This picture below shows the front of the engine and the side of the crank that receives the magneto. Install the starter ring gear. (blue arrow)

Install the rear balancer and align the timing marks between the balancer and magneto in the same manner as above. Tighten the magneto finger-tight only. [FIG 26]

[FIG 26]
View attachment 624922
With the crankshaft now inserted into the upper crankcase, 2 cycle engine oil in the front balancer cavity and the timing marks aligned on both front and rear balancers with their respective gears and the crank bearing and coupler indexing pins aligned and sitting in their slots [FIG 27], slowly spin the crankshaft by hand to check for freedom of movement.

If you have constructed your wooden ‘T’s with enough height, the connecting rods will spin freely and not hit the work bench top.

Make sure the rear balancer does not fall out during this test as it is held only with one bearing at this point.

If everything appears to spin freely, you are ready to move on to the next step.

Ensure the index pins have not moved, the balance gears have not become misaligned or out of time and the oil seals are seated properly.

Ensure the two middle crank bearing snap rings (red arrow) are seated in their respective grooves.

Ensure the bottom crank case half has been prepped and cleaned and ready to lift into place.

Oil the crank and lower rod bearings.

If all of the above is good to go; apply a continuous bead of liquid gasket (I use Permatex®

Grey applied with a spreader to get max coverage) maker to the mating surface and set the lower crankcase half into place.

[FIG 27]
View attachment 624930
Do not force the case half in place. It should drop relatively easily into place and with the exception of a small gap which will close once you compress the oil seals, it should be almost a perfect fit. Do not forget to ensure the connecting rods are hanging through the upper crank case half. [FIG 28] You now have 30 minutes before the gasket maker starts to set up to torque the fasteners.

Note: Before continuing with the torque procedure, place the first four (4) middle main crank bolts [FIG 29] in place and snug up. (do not force) If the crank can be spun freely by hand, continue. If your procedure calls for a locking agent on the bolts, do so. (I used blue LocTight® sparingly on mine)

Follow the torque procedure outlined in your service manual.

Install the rear balancer bearing cap. (red arrow)

[FIG 28]
View attachment 624938
[FIG 29]
View attachment 624946
After you have completed the torque sequence, remove any excess gasket maker at the seams. (red arrow) [FIG 30]

Proceed to install the intake studs using the two bolt method described above and whatever the manufacture suggests regarding locking agent. In my case I used blue LocTight®) (blue arrow) [FIG 30]

Install the starter (ensure you apply a small amount of grease on the ‘O’-ring to ease installation) [FIG 31]

[FIG 30]
View attachment 624954
[FIG 31]
View attachment 624962
Proceed to install the intake reeds using new gaskets both front and back. [FIG 32]

Next install the intake manifold but remember; place the balance tube at the bottom which will be correctly installed at the top once the engine is turned over. [FIG 33]

Note; There is a correct direction to install the reeds. Ensure you have the reed properly placed in the down position. This will place it in the up position once you turn the engine over. Remember that this engine is still upside down at the present time and the top is presently on the bottom.

[FIG 32]
View attachment 624970
Once the intake manifold has been properly torqued, you may flip the engine right side up. [FIG 33]

[FIG 33]
View attachment 624978
With the engine now sitting correctly orientated in the upward direction, you may place the cylinder base gaskets in place (Black). (red arrow)[FIG 34]

At this point you may be wondering why we installed the front balancer, starter ring-gear and magneto as this could have been installed after the crank case was closed.

I prefer to do it my way because it ensures that the items mentioned above are in correct alignment with their respective mating parts and the fit appears proper. A pre-assembly exercise if you will.

[FIG 34]
View attachment 624986
Be sure to place either clean rags or paper towels in the intake areas of each port and the areas where the connecting rods protrude through the upper crank case half. You do not want anything falling into these areas. [FIG 35]

Install the piston rings on the pistons, at least one wrist pin clip on one side of each piston and push the wrist pin into the wrist-pin hole on the opposite side until it is just starting to appear through the piston hole in the underside.

Lubricate the upper small ends of the connecting rods and install the pistons, wrist-pins and bearings making sure that each wrist pin clip is properly seated in it’s respective groove. (follow your service manual regarding)

Slather oil on each cylinder wall, piston and ring set, align the index pins in the ring grooves to the ring set, compress the rings by finger tension and gently ease the piston into the cylinder from the bottom. It’s a bit tricky but rocking the cylinder a bit in either direction will nudge it home. [FIG 35]

Once the piston is in the bore of the cylinder, you should easily be able to slide the cylinder over the piston and seat it on its mounting place upon the upper case. Take special care to protect the other pistons when performing this task.

Repeat the above for the other two (2) cylinders. [FIG 36]

[FIG 35]
View attachment 624994
[FIG 36]
View attachment 625002
You may install the cylinder base mounting bolts at this point following your service manual procedure. (red arrow) [FIG 37]

At this point, spin the crank by hand just to ensure everything feels as it should. If it does, place plastic ties at either ends of the balance tube and secure. (blue arrow) [FIG 37]

Install the head gaskets and ensure you place clean rags or paper towels in the exhaust ports of the cylinders. [FIG 38]

[FIG 37]
View attachment 625010
[FIG 38]
View attachment 625018
At this time, I install the water manifold following the service manual torque procedure. [FIG 39 & 40]

[FIG 39]
View attachment 625026
[FIG 40]
View attachment 625034
Then comes the exhaust manifold and carburetors following the service manual torque procedure. [FIG 41 through 47]

[FIG 41]
View attachment 625042
[FIG 42]
View attachment 625050
[FIG 43]
View attachment 625058
[FIG 44]
View attachment 625066
[FIG 45]
View attachment 625074
[FIG 46]
View attachment 625082
[FIG 47]
View attachment 625090
Shown previously; this figure below [FIG 48] shows an important area and specifically; the location of an ‘O’-ring. This ‘O’-ring did not come in the gasket kit but is very important as it self locates the correct positioning of the seal collar shown above at the red arrow.

Failure to install this ‘O’-ring will cause the crank case to leak oil profusely and destroy the seal. The collar fits snugly over the ‘O’-ring prior to torqing the driven shaft coupler. Ensure this is installed.

I purchased one from Canadian tire®

[FIG 48]
View attachment 625098

In figure 49, I have just installed the oil injection lines and pump. (red circle) Ensure you use a suitable means to secure the oil line to its attachment point (in this case I have used plastic ties) to ensure any oil line does not inadvertently fall off. It’s a good idea to replace the lines at this point as they are known to fail after time. (crack)

I have also torqued the magneto bolt.


After torging the magneto bolt, it is imperative that you test the one-way starter ring gear clutch (red arrow). Do this by rotating the magneto in the clockwise direction using a power bar or ratchet and socket. Watch the starter reduction gear (blue arrow). If the gear does not rotate at this time, the clutch is working as it should and the clearance is correct between the back of the magneto and the thrust washer ahead of the starter ring gear.

If the starter reduction gear turns along with the magneto, you have a problem! (as was the case with mine)

Because my crank was sent out to be reconditioned, it is possible that the rebuilders polished the magneto end of the crank with emery paper and if this is done, it is possible to reduce the size of the taper on the crank end. Reducing the taper by even a few thousands of an inch will allow the magneto to set back closer to the thrust washer and place pressure on it casing the starter ring gear to bind.

If this binding is not corrected, when the engine starts, the starter ring gear will spin the starter reduction gear and thus the starter itself to insane speeds and will likely destroy the starter.

To correct the clearance, you will need to reduce the thickness of the thrust washer behind the magneto. I accomplished this using a grinder with an 80 grit grinding disk.

[FIG 49]
View attachment 626738
Here we see the exhaust installed along with the fuel primer lines secured (blue arrow figure 50 & 51)

[FIG 50]
View attachment 626746
[FIG 51]
View attachment 626754

Let’s go ahead and torque the magneto to 90 foot lbs. (red arrow) [FIG 53]

[FIG 53]
View attachment 628490
Figure 54 will see the head bolt torqued. (red arrow)

[FIG 54]
View attachment 628498
In figure 55, we will now torque the magneto cover to the engine block. (red arrows)

[FIG 55]
View attachment 628506
After you have torqued the mag cover, you can fill the case with 2 cycle engine oil but only to the half way mark in the viewing glass and at the plane shown by the blue arrow. [FIG 56] This is the plane that the engine will be at when mounted in the hull of the watercraft. In this case I have used synthetic 2 cycle oil.

[FIG 56]
View attachment 628514
Now we torque the driven coupler. [FIG 57] (red arrow)

[FIG 57]
View attachment 628522
Finally, we prime the oil pump by gravity feeding 2 cycle oil into the opening marked at yellow arrow and then install and torque the spark plugs and you my friend are ready to drop this puppy in the hull! [FIG 58]

[FIG 58]
View attachment 628738

I hope you have found this article helpful and enjoyable to read.

I thank you for taking the interest in reading it.



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