ProX takes you through the major parts of rebuilding a four-stroke top end, complete with step-by-step guides for each task along the way!
In the simple two-stroke days of riding and racing, rebuilding a top end was just a matter of slapping a new piston and rings in, maybe with a little cylinder cleanup thrown in for good measure. There were no camshafts, timing chains, or valves to worry about. The vast popularity increase of four-strokes added a whole new handful of moving parts to worry about when rebuilding a top end. However, rebuilding your four-stroke doesn't have to be as intimidating as it may seem.
Referring to the "top end" of a four-stroke is generally referring to the piston, cylinder, and head, including all the components the head houses. The head of a four-stroke houses your key valvetrain components, such as camshaft(s), valves, valve springs, and the other small components that help the valvetrain function properly.
Four-Stroke Top End Rebuild Steps
A four-stroke top end rebuild will consist of two major parts. Check out the links below to see ProX's complete how-to guides and videos on each part of your four-stroke rebuild:
Replacing and Installing Valves
If your engine has a good amount of time on it, there's a chance you may determine that you need to replace your valves, valve springs, and other valve components after inspecting the head. Routinely checking these items with top end maintenance can help prevent expensive failures and, with a little guidance, does not have to be an intimidating process.
Following these guides should get you through each critical step in freshening up the top end in your four-stroke. Performing maintenance like top end replacements yourself can save a lot of money in labor, but it's also important to make sure you're sourcing reliable and affordable parts. ProX prides themselves in providing OEM-or-better quality parts, many manufactured by OEM suppliers themselves, at a budget-friendly price. Want to see more on ProX four-stroke pistons? Check out all the details on materials and manufacturing here.
If you rebuild your four-stroke top end and there seem to be some performance issues, there's a number of other things that could require attention—everything from the clutch to the cooling system to bottom-end components. It's important to know the common signs of a tired engine.
ProX is not just committed to providing high-quality performance replacement parts, but the ProX crew are also riders themselves, and they want to help fellow riders and racers with as much support as possible. With technical articles on everything from brake systems to clutch replacement to throttle cables, ProX supports riders and their maintenance needs from axle to axle. Browse the ProX blog and bookmark any articles you find most helpful.