Cylinder Heads
About Cylinder Heads
The cylinder head closes the top of the cylinder and forms the combustion chamber, and on four-stroke engines it also holds the valves. This category has parts for particular machines: cool heads and cool domes for two-stroke quads such as the Honda ATC250R and TRX250R and the Yamaha Banshee, head shells in black or polished finish, head nuts, service kits and a Honda head kit.
Domes are listed by volume in cubic centimeters, and in race gas or pump gas versions. A smaller dome volume raises compression, so the engine needs the fuel the listing is meant for. Match the version to the fuel you will run, and check that the part is listed for your engine. Tighten head nuts evenly, in the pattern and to the torque your manual gives, and fit a new head gasket or the sealing parts your engine uses whenever the head comes off. Service kits differ, so read the listing for what is included.
Brands in this category include Pro Design, Kibblewhite, ModQuad, Cylinder Works and KPMI. Pick your machine in the Ride Finder at the top of the page. Related pages are Complete Cylinders, Gaskets, Seals & Kits, Pistons, Rings & Piston Kits and Engine Covers, all part of Engines & Engine Parts.
FAQs on cylinder heads and domes
What does dome volume mean?
Dome volume is the size of the combustion chamber in cubic centimeters. A smaller volume squeezes the mixture into less space, which raises compression. Higher compression usually needs higher-octane fuel, so choose a dome that suits the fuel you will actually use.
Can I use pump gas with a race gas dome?
Check the listing. Domes are sold in race gas and pump gas versions because they set different compression. A version made for race fuel used with pump gas can cause detonation, which damages the engine. Choose the version for your fuel.
In what order should I tighten cylinder head nuts?
Follow the pattern in your service manual, normally working across the head in stages and finishing at the specified torque with a torque wrench. Tightening the nuts evenly helps the head seal and prevents warping.
Do I need a new head gasket whenever I remove the head?
Yes. Head gaskets and sealing rings compress when tightened and do not reseal reliably when reused. Use a new one, clean the mating surfaces without gouging them, and check the surfaces for flatness before assembly. The right gasket for your engine comes from the listing for your make and model.
