Cylinder Heads
About Cylinder Heads
The cylinder head caps the cylinder and holds the valves, the combustion chamber and, on most engines, the spark plug. Riders shop for one when a head is cracked, warped or worn at the valve seats, when an engine is being rebuilt, or when a performance build calls for a head that flows better than the stock casting.
A head has to match the engine family and the cylinder it bolts to, so start with the exact model and year, or on Harley-Davidson builds with the engine type, such as Twin Cam or M8. Performance heads are listed with a combustion chamber size in cc, and that number should suit the pistons and cylinders you are running. Read each listing to see whether valves, springs and guides are included, because a bare casting needs them before it can run. Cylinder head service kits are also listed here for specific off-road models such as the Yamaha YZ450F, Honda CRF450R and Kawasaki KX250F; the listing shows what each kit contains.
If you are unsure about compatibility, our guide why a part didn't fit explains how to check. Brands in this category include S&S Cycle, Race Tech, Kibblewhite, Cylinder Works and Pingel. A head swap usually means new gaskets from Gaskets, Seals & Kits and fresh hardware from Cylinder Bolts. If the cylinder needs work too, see Complete Cylinders.
FAQs on motorcycle cylinder heads
What is the difference between a cylinder head and a cylinder?
The cylinder is the bore the piston travels in. The cylinder head sits on top of it, closing the bore and holding the valves and spark plug. On many engines the two are separate parts sold separately, and each must match the other.
Do I need a new head gasket when I fit a cylinder head?
Yes. A head gasket is crushed when it is tightened and should not be reused. Fit a new one, clean both mating surfaces, and follow the service manual for the bolt tightening order and torque.
What does the cc number on a performance cylinder head mean?
It is the volume of the combustion chamber. A smaller chamber raises the compression ratio when everything else stays the same, so the figure has to be worked out together with the piston and cylinder. Follow the head maker's guidance for your engine.
Can I fit a cylinder head from a different year of the same model?
Not safely without checking. Port shape, bolt pattern, sensor positions and valve sizes can change between years. Use the listed fitment, or pick your machine in the Ride Finder at the top of the page, and compare part numbers.
What else should I look at while the cylinder head is off?
Check the valve seats, valve guides and springs, the head and cylinder mating surfaces for flatness, and the head studs or bolts. Some bolts are single-use, so check the service manual before reusing any hardware.
