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Kawasaki 903/1015cc Valve Clearance Adjustment

Why do valve clearances grow less over time?

The bucket atop the valve stem is depressed when the cam lobe actuates it. This pushes the valve down through it’s guide and the face leaves the closed position where it contacts the valve seat and pushes the valve face down into the combustion chamber area to open that valve. As the cam lobe rotates, the valve then closes; that is, the face of the valve comes back into contact with the seat. This return action is caused by springs in the valve assembly (not shown). Where the face of the valve contacts the seat, the seat tends to wear over time. Neither the cam lobe, valve stem or face tend to wear as wear is concentrated in the valve seat (seen in the drawing in red). When the seat wears, the valve stem tends to protrude farther upwards (the bucket is on top the valve stem). This causes the clearance between the valve bucket and cam lobe to decrease over time.

Once valve clearance between the valve stem and cam lobe disappears and the cam lobe is in actual contact with the bucket, the valve will stay a bit ajar (open). Compression is lost and eventually, a zero PSI compression state will exist in that cylinder. Combustion can not take place if there is reduced or no compression.

Why Adjust Valve Clearances?

Properly adjusted valve clearances are necessary so that the valves will open and close as they should. Cylinder head valve seats wear from the contact with valves that move on every turn of the crankshaft. The clearance between the cam shaft lobes and valve shims lessen over time. If there is insufficient clearance, the valves can remain open during combustion and power will be lost. Engine damage can result if valve clearances are not adjusted as needed. There is a maintenance schedule in your factory shop manual or Clymers. Generally, clearances do not change rapidly so while checking is needed at periodic intervals, actually changing shims, which is the heart of setting valve clearances is done fairly infrequently. If valve clearances are too wide, the valves can be very noisy and as clearances close, the valves tend to get progressively quieter. If you don’t hear your valves at all, this is a sure sign that you have insufficient valve clearance.

Tech Specifications

1973-1978 clearances from 0.05-0.10mm are acceptable. 1979/80 clearances 0.05-0.15mm are acceptable.

If you are not sure which cylinder head is on your bike, the earlier heads have 6mm studs and later have 8mm studs. In addition, many of the later heads are “smog heads” where there are passageways from the combustion chambers up to rear of the exhaust valves. The valve cover used on these heads will have the reed valves and smog ports where hoses are attached. The smog heads all have 8mm studs.

Step 1

Disconnect your battery. Remove the spark plug leads from the spark plugs and tape them out of the way. Remove the spark plugs. Remove the bolts that hold the valve cover on and remove the valve cover. If you have a “smog head”, remove the reed valve covers. The manual may call for removing your coils. This is NOT necessary on most models. To get the valve cover off, lift it and move it to the rear so the cam chain idler assembly doesn’t contact the cover as you slide it out the side.

If you have not removed the valve cover recently or don’t know how long it has been in place, the valve cover gasket may tend to break and stick to the mating surface. It is a good idea to have a spare gasket ready in the event the old one breaks.

It is a great idea to torque the cam cap bolts prior to making clearance measurements. In the event any are not torqued properly, the measurement you make WILL be WRONG!!! The early cylinder head is about 9 lbs. and the later is about 12 lbs. Consult a torque table in your manual for all torque specifications.

Step 2

Measure clearances and write them down. To measure, you will need a good quality feeler gauge as cheaper ones won’t have the thinner gauges needed to make the measurements. I use one I got from Craftsman and it is a metric gauge. You can make measurements in inches but metric measurements are easier as shims are measured in millimeters. Everything in metric makes computing the correct shim easier.

Make sure the feeler gauges don’t stick together. They are thin and the oil they pick up will tend to make them cling together.

While sitting on the right side of the bike, note markings on the cam sprocket on the intake camshaft. The intake camshaft is toward the rear of the bike. There are two marks that must be oriented horizontally and inline with the valve cover gasket. To move the camshaft and thus the marks, you rotate it by turning the 17mm nut on the end of the crank shaft. It is the nut closer to the engine. The outer and smaller nut is too weak for turning and if used, will just break off. Rotate the engine so the marks on the camshaft sprocket align with the valve cover gasket.

With the lines on the camshaft sprocket aligned as above, you can measure two of the intake valve clearances. These will be either 1 and 3 or 2 and 4. The pair that can be measured is the pair where neither has a cam lobe pressuring a shim. You should be able to put a feeler gauge between the shim and camshaft and feel a slight pull. You shouldn’t have to force the gauge between the two surfaces. Use the appropriate sized feeler gauge to get this slight pull.

A “smog head” type cylinder head for these pictures. In the picture above, if you are observant, you will have caught that the clearance is .178mm which exceeds the allowable for the later style cylinder head. The result is noisy operation but not enough clearance where there is danger from running the bike, as is. We will change shims in a later step. The size of the feeler gauges correspond to one shim size (.05mm), approximately.

Now that you have two valve clearances on the intake cam measured, turn the 17mm nut on the end of the crankshaft one turn so that the intake camshaft turns 180 degrees and the marks on the intake camshaft sprocket once again align with the gasket surface. Measure the other valve pair the same way and write down all clearances. Repeat these steps for the exhaust camshaft.

Step 3

Some valve clearances will be within specification and some may not be. You saw an example of a valve with too much clearance in the previous step. Some Kawasaki Factory Service Manuals list a chart showing the existing shim versus the measured clearance and tell you which shim to use. Such a chart is fine to use but you should also understand how to determine which shim is needed. In the case above, .178mm clearance was measured. There was a 270 shim in the bucket at the time of the measurement (2.7mm). To figure out which shim is really needed to get the correct clearance you must understand that a 270 shim is 2.70mm. Do the math:

If 2.7mm (270 shim) gives you .178mm clearance 2.75mm (275 shim) will give you .128mm clearance which is within specification. You subtract .05 (difference in shims) from .178:
.178 - .05 = .128mm clearance

As an example, if you measure clearance at .052mm using a 270 shim and want to increase clearance to .152mm which is the maximum allowable, do the math:

Add clearance by using a thinner shim. Using a 265 shim (2.65mm) will add:

.052 + .05 = .102mm

SO, an even thinner 260 (2.60mm) shim will give you:

(original clearance with 270 shim) + 1 (up two 1/2 mm shim increments using a 260 shim) = .152mm (new clearance)

OK, now that you have computed which shims are needed, where can you get the shims? Can you swap any of the shims that will be coming out for change? If you need new shims, a few Kawasaki dealers MAY have them and be willing to trade or sell you the shims needed. If a dealer does sell shims, they may want as much as $11 per shim. It is frequently more cost effective to contact for a kit of shims or the specific shims you need. If you plan on keeping the bike, the kit is more economical in the long run as it contains a sampling of shims of various sizes.

If you can not measure clearance, but CAN spin the bucket when the lobe isn’t pressing down on the shim, there is clearance. You just don’t have a feeler gauge thin enough to make the measurement. It is helpful to have a 2.00mm (200) shim which can be swapped out for your current shim to make the initial clearance measurement.

Step 4

Now, you have found that some of your clearances are outside specification and have secured the needed shims to make the clearance adjustments, you will also need a Kawasaki factory “Valve Lifter Holder P/N 57001-113” or you can buy a Motion Pro valve shim tool which consists of two parts. One is a hooked lever bar with a ball end for easier grip and the other is a double moon shaped piece that fits under the edge of the camshaft and along the edge of the bucket to hold the bucket down once pried down with the latter described part of the tool. The genuine Kawasaki tool works far more easily. The following steps describe use of the genuine Kawasaki tool for changing shims.

To change the shim, first rotate the crankshaft so that the cam lobe points away from the shim. Rotate the bucket so that the notch faces towards the opposite camshaft. This will make it far easier to remove the shim later. 

Rotate the crankshaft so the lobe on the camshaft adjacent to the valve that needs clearance adjustment presses DOWN on the shim to be removed. Place the Kawasaki Valve Lift Holder tool into position so that it’s edge will contact the edge of the bucket. Rotate the crankshaft away from the tool using the 17mm nut on the crankshaft end and the lobe of the camshaft rotate so that it points directly away from the shim now. If the tool was placed correctly, the bucket will not rotate but will be held down and in place. Use a fine dental pick to pry under the shim. Hydrostatic tension will want to hold the shim in the bucket. It is sometimes helpful to have a magnet to fish the shim out or use a pair of tweezers or fine needle nose pliers to remove the shim once you have the dental pick under the shim a bit.  Once the old shim is out, replace it with the new shim of the correct thickness.

Step 5

Put things bacl together in the reverse order they were taken apart.  It is suggested you remeasure clearances after making adjustments.  Good Luck!

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