In general, the engine of a motorbike should be replaced every 15,000 km or after an engine failure. If your engine is damaged, you will have to replace it. But how do you replace a damaged motocross engine? Find out in this article how to change a motocross engine.

Materials needed to replace a motocross engine

For the replacement, disassembly and assembly of a motocross engine, you need the following tools: a piston, a needle cage, coolant, a T-wrench, a screwdriver, a set of original gaskets. These devices should be original. But in case you can't find an original tool, you can use an equivalent from another brand.

Disassembly first

First you have to dismantle the seat, the fairing and then the tank. But in the other motocross model, it is not necessary to remove these parts. To avoid dirt on the engine when you touch it, don't hesitate to take a swipe at the bike. After the seat, fairing and tank are removed; remove the bleed screw to open the radiator cap. Then drain the coolant from the radiator and replace it. To prevent the coolant from leaking when you refill it, replace the front bleed screw. Next, loosen all the cylinder head screws to remove it. Afterwards, unscrew the cylinder screws so that you can remove it. For better handling, put a rag below the engine. This will help you easily collect the piston clips that you have dropped. This way you don't have to dismantle the whole engine to retrieve the piston clip. If you have retrieved the piston clip, take it apart and move the piston pin. Then remove the piston and needle cage. Afterwards, clean all the seal faces and parts you removed. When everything is clean, proceed to reassembly.


First, the piston should be replaced. Put the clip and the ring on the piston. Then place the needle cage and the piston on the connecting rod head. Markings will help you not to mount it upside down: the angle should go up to the side of the intake or the arrow that points to the exhaust. Next, fit the piston pin. For an easier fit to your engine, lubricate the parts with oil. Also change the engine seals. After that, replace the cylinder and put some grease inside. Then, put the piston inside. Next, tighten the cylinder nuts. Reassemble the cylinder head with the new gaskets. Finally, fit the radiators (with new coolant), the tank and the fairings.