Engine Rebuild Kits & Components
About Engine Rebuild Kits & Components
Rebuild kits gather the parts that wear inside an engine so they can be ordered together: pistons, rings, gaskets, cylinder kits, crankshaft kits and, in some listings, a full set for the whole engine. Riders look here when an engine has lost compression, burns oil, or is due a refresh, which is routine on race-used dirt bikes and small two-strokes.
Decide how much of the engine needs work. A top-end kit, such as a piston kit with gaskets, deals with the piston, rings and cylinder wear. A crankshaft kit or a complete engine rebuild kit covers the bottom end as well. Harley-Davidson listings here include camshaft kits and power packages, which are performance upgrades more than repairs. Piston kits are listed by bore, such as 40.00, 47.50 or 68.50 mm, and by standard or oversize, so measure the cylinder and match it. Always check the model and year, since two-stroke and four-stroke versions of one bike are not interchangeable.
Brands here include Athena, Vertex, Hot Rods, Millennium and S&S Cycle. Pick your machine in the Ride Finder at the top of the page. Related categories are Gaskets, Seals & Kits, Crankshafts, Complete Cylinders and Engine Bearings.
FAQs on engine rebuild kits
What is usually included in a top-end rebuild kit?
A top-end kit normally has a piston, rings, a wrist pin and clips, and gaskets, and some add a cylinder. Contents differ between listings, so read the description to see what is and is not in the kit.
How do I choose the right piston size for my cylinder?
Measure the bore at several heights with a bore gauge or micrometer and compare it with the wear limit in the service manual. If it is within limits, use a standard size. If the cylinder is machined, order the matching oversize piston.
How do I tell whether I need a top end or a bottom end rebuild?
Low compression, smoke and piston wear point to the top end. Knocking from low in the engine or play in the crank points to the bottom end. A compression test and inspection against the service manual confirm which.
What should be done before installing a new piston kit?
Clean the cylinder and cases, inspect the bore for scoring, measure clearances, and check the cylinder is not damaged. A scored cylinder may need replating or replacement instead of just new rings, so look before you order a piston.
Does a rebuilt engine need a break-in period?
Yes. New rings and bearings need to seat, so vary engine speed, avoid full throttle at first, and follow the break-in steps from the kit maker or the manual. Many riders change the oil soon after.
