Classic Motorcycle Build

Kawasaki KZ650 Adjust Valve Clearance

Article and Pictures by Mark Trotta

If you weren't the last tech to adjust valve lash on a DOHC Kawasaki, you may be in for a few unwelcome surprises. On this low-mileage '77 KZ650, I encountered over-tightened bolts and stripped threads.

Kawasaki KZ650 1977

After the proper shims were installed, lost power was restored, the bike runs smoother at all speeds, and it's much easier to start when cold.

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This article covers adjusting valve lash on Kawasaki KZ650 models.

KZ650 correct valve clearance

Click here for step by step procedure on how to check valve clearance.

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Shim Under Bucket

In a DOHC Shim Under Bucket design, an inverted “bucket” (valve follower) sits over the top of the valve, underneath the camshaft.

remove camshaft Kawasaki KZ six fifty

Underneath the cams, and underneath the buckets, there are small round shims that are available in different thicknesses. If valve clearance is too small or too large, shims can be swapped out for larger or smaller sizes.

Kawasaki KZ650 valve bucket with shim in place

Pictured above is a valve bucket sitting upright with shim still in place.

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CAUTION: If you're in doubt as to your abilities to check and adjust valve clearance, consider bringing your bike to a shop or dealership. A well-intentioned DIYer can do serious damage!

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Adjusting Valve Lash

Technically, you're not “adjusting” anything--if valve lash is out, the shim is replaced with one of a different thickness. If clearance is too small or too large, shims are available in larger and smaller sizes.

Although valve shims can be purchased individually, buying a valve shim kit is usually more practical. Besides being more price effective, it gives you a margin of error when you calculate wrong.

13mm valve shim kit

This shim kit was purchased from Z1 Enterprises in Florida. For $85, you get 20 different-sized shims, which works out to $4.25 apiece.

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To actually get to the shims and valve buckets, the cam(s) have to be lifted up and out of the way.

Procedure To Remove Cams

Follow the procedure on how to check valve clearance. This will include removing the gas tank, coils, and cam cover.

Kawasaki KZ six fifty cylinder head cover

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The KZ650 has upper and lower cam chain tensioners. During the valve adjustment procedure, they need to be removed so that tension is taken off the chain.

Remove Upper Cam Chain Tensioner

The top tensioner is removed with four 5mm Allen bolts.

Kawasaki KZ650 correct valve lash

CAUTION: Do not drop any of the tensioner parts into the open crankcase!

adjust valves on Kawasaki KZ six fifty

Remove Lower Cam Chain Tensioner

On early KZ650's, the lower chain adjuster is automatic. Two bolts (10mm wrench) hold it to the back of the cylinder.

lower cam chain tensioner Kawasaki KZ

It's a tight squeeze, but I was able to remove the two bolts by first using a long wrench (for torque) and a then short wrench (for clearance).

Kawasaki KZ timing chain tensioner

Lower tensioner removed.

lower cam chain tensioner Kawasaki KZ six fifty

Tachometer Cable

The tachometer cable unscrews from the front of the cylinder head with a round knurled fastener. Light pressure with a pair of Channel Lock pliers is all you should need to loosen it.

Kawasaki KZ tachometer cable

Remove Cam Caps

Cam cap bolts are removed with a 10mm socket.

best way to always find the correct size tool

About the green tape on the socket. I never have to look too hard to find my 10mm socket. It's the one with the green tape on it.

Over-Tightened Bolts

Loosening over-tightened bolts is always scary, especially when they're in a precision-machined aluminum head. On this motor, all 16 cam bolts were previously over-tightened, with two of them stretched to the point of distortion. By loosening slowly and carefully with a small 1/4" drive ratchet, I lessened the chance of any of them snapping.

adjust valves Kawasaki KZ DOHC

While loosening the caps, the cams will start rising up off their perches. This is normal and OK, it's just valve spring pressure under the cams.

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Camshaft Removal

You don't necessarily have to take the cams off the engine to get to the cam buckets. With both chain tensioners removed, there's enough free-play in the chain to move the cam and have access to the buckets.

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Roll Camshaft Out Of The Way

Without taking the chain off the gear, you can 'roll' the cam away from it's perch, change the shim(s) in question, then roll the cam back onto it's perch.

lower cam chain tensioner KZ650 move cam without taking chain off

By using this method, you never lose chain placement.

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Before proceeding, take a moment and look across the top of the cylinder head.

camshaft removal KZ650

Do any of the valve buckets sit further down than the others?

If so, it's a sign of a badly worn seat, bent valve, or perhaps broken spring.

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Remove Valve Buckets

To remove the cam buckets, you'll need a valve lapper tool, which is basically a plastic or wooden dowel with a suction cup on the end.

remove cam buckets with valve lapping stick

If needed, squirt a few drops of oil on the top of the bucket.

valve lapping tool to remove cam followers

Rubber cups stick well to oily buckets.

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Valve Lash Specs

To get the valve lash into the recommended range, you first have to determine what size shims you need. If you can't read the numbers on the old ones, measure them with a digital caliper.

The factory service manual includes a chart, which tells you which shim to use to achieve recommended clearance. Or you can just do the addition/subtraction on a piece of paper.

On this 1977 Kawasaki KZ650, valve lash specs are 0.008mm to 0.018mm. My factory manual is for early models, it's best to check your exact year and model.

After getting the cam shims right, during final torquing, one of the cam bolt threads stripped. This led to very carefully drilling out and inserting a 6mm Helicoil insert.

Read: Repair Stripped Threads In Aluminum

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Finally, time to button up the motor.

Cam Cap Installation

Before reinstalling the cam caps, apply a few drops of engine assembly lube.

best engine assembly lube for motorcycle

In case you forget where the caps go, from left-side of bike to right-side, numbers 1, 2, 3, and 4 are exhaust (front cam), while 5, 6, 7, and 8 are intake (rear cam).

Kawasaki KZ650 install cam caps

The factory service manual recommends 92 to 113 inch-pounds for cam bolts, which is quite high for a 6mm bolt. After my experience with the stripped bolt, I won't torque any higher than 100 inch-pounds.

There is a recommended sequence to tightening cam cap bolts, which is generally inner to outer. Once they are all hand-snug, torque equally to 60, then 80, then 100 inch-pounds.

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Notes and Misc

On early Kawasaki KZ650 models, the factory service manual recommends checking valve clearance every 5,000 kilometers, which is about 3,100 miles.

Kawasaki KZ650 factory service manual

The FSM will let you find answers quickly and accurately.

Adjusting valve clearance restores lost engine performance and helps eliminate unwanted noise. On this '77 KZ650, it also solved the hard-starting issue.

Kawasaki KZ DOHC engine repair

Proper valve clearance is also inexpensive insurance against future engine problems.

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