Valve clearance is the small gap between the valve train and the valve stem when the valve is fully closed. That gap exists so the valve can seat completely as engine components expand with heat, and it changes over time as the valve and seat wear into each other. Most manufacturers specify a check every 8,000 to 16,000 miles, and the interval is in your manual along with the exact figures.
The job takes a few hours, needs modest tools, and saves a substantial shop bill. Here’s how it works.
Why Clearance Matters
As valves and seats wear, the valve sits deeper in the head, which reduces the clearance. Too little clearance means the valve never fully closes, so combustion gases escape past the seat, the valve loses its main path for shedding heat, and a burned valve follows. That repair means a top-end teardown.
Too much clearance is less destructive but still costly in performance. The valve opens later, closes earlier, and moves less than designed, which costs power and produces the tapping sound people associate with loose valves. Symptoms of tight clearances are harder to spot and more dangerous: hard starting, especially when cold, and a slight loss of power that develops so gradually you may not notice it.
What You’ll Need
- A feeler gauge set, ideally with blades in the range your bike specifies
- Metric sockets, wrenches, and Allen keys for the covers
- A torque wrench for reassembly
- New valve cover gasket if yours is not reusable, plus any O-rings the procedure lists
- For shim-type engines, the correct shims, which usually means measuring first and ordering after
- The service manual for your exact model
Getting To The Valves
Work on a stone cold engine, since clearances are specified cold and a warm engine gives false readings. Leave the bike overnight if it has run that day.
Access varies by bike. Most require removing the seat, tank, and any fairing panels covering the head, then the ignition coils or spark plug leads, and finally the valve cover. Remove the spark plugs as well, which lets the engine turn over easily by hand. Keep the fasteners organized as you go, since valve covers often use bolts of several lengths.
Finding Top Dead Center
Clearance is measured with the cylinder at top dead center on the compression stroke, when both valves are fully closed and the cam lobes point away from the valve train.
Turn the engine over by hand using a socket on the crankshaft bolt, always in the direction of normal rotation, until the timing marks align. Most engines have a mark on the rotor visible through an inspection port, and the cam sprockets carry their own marks that should align with the head surface or a casting line. The manual shows exactly which marks to use, and on multi-cylinder engines it lists the crank positions for checking each cylinder in turn.
Measuring The Gap
Slide the feeler gauge between the cam lobe and the follower, bucket, or rocker, depending on your engine design. The correct blade slides in with light drag, meaning slight resistance without forcing. If it goes in freely, try the next size up. If it won’t enter at all, work down.
Record every measurement against its valve, noting intake and exhaust separately, since they carry different specifications. Do this even for valves within spec, because the record tells you how fast each valve is closing up when you check again in another 10,000 miles.
Making The Adjustment
Two designs cover almost all motorcycles.
- Screw and locknut systems, common on many singles, twins, and older bikes, adjust in place. Loosen the locknut, turn the adjuster until the feeler gauge has correct drag, hold the adjuster steady and tighten the locknut to its torque figure, then measure again, since the setting frequently shifts as the nut tightens.
- Shim under bucket systems, standard on most modern multi-cylinder engines, require replacing a hardened shim with one of a different thickness. This means removing the camshafts on most designs, so the timing chain has to be secured and the cams reinstalled with their marks correctly aligned and their caps torqued in the specified sequence. The arithmetic is straightforward: existing shim thickness, plus measured clearance, minus target clearance, gives the new shim size. The care required is in the camshaft removal and timing, which is why the procedure for your specific engine matters more here than anywhere else in the job.
Reassembly
Reinstall the valve cover with a new gasket if needed, torque the fasteners in the sequence and to the figure given, and reconnect everything in reverse order. Turn the engine over by hand through two full revolutions before starting, which confirms nothing binds. Start the bike, listen, and check for oil leaks around the cover once it reaches temperature.
Get The Figures For Your Exact Engine
Clearance specs, timing mark locations, torque values, and shim calculations differ between models and even between years of the same model. At emanuals, our community members have direct access to hundreds of motorcycle workshop manuals online, covering everything from current sportbikes to machines the dealer network stopped supporting decades ago. Sign up today and check your valves with the same figures the factory technicians use.
FAQs
How often should motorcycle valve clearances be checked?
Most manufacturers specify an interval between 8,000 and 16,000 miles, though some cruisers and singles call for more frequent checks and some modern bikes stretch further. The figure for your model is in the maintenance schedule in your manual.
What happens if valve clearance is too tight?
The valve cannot close fully, which lets combustion gases past the seat and removes the valve’s main cooling path. The result is a burned valve and a top-end rebuild, which is why tight clearances are the more serious direction of error.
Can I check valve clearance on a warm engine?
No. Specifications are given for a cold engine, and thermal expansion changes the readings enough to make warm measurements useless. Let the bike sit overnight before starting the job.
Do I need to remove the camshafts to adjust valves?
Only on shim-under-bucket engines, where the shim sits beneath the cam. Screw and locknut systems adjust in place with basic hand tools, which makes them considerably faster to service.
How do I know which shim size to order?
Take the thickness of the shim currently fitted, add your measured clearance, then subtract the target clearance from the manual. The result is the new shim thickness, and most people measure every valve first so they can order all the shims they need in a single purchase.