How To Remove An Engine
From A Dirt Bike
Occasionally it's necessary to remove an engine from a dirt bike's frame to perform necessary repairs. However, a large percentage of commonly performed engine work from replacing the top end to servicing the clutch, or even replacing a clutch basket can almost always be accomplished without removing the engine from the chassis, although engine work which does require separation of the engine cases such as transmission or crankshaft services is simply not possible without removing the engine from the motorcycle.
If the bottom end is worn out (locked up, knocking, rattling, vibrating, case damage etc...), or the motor has transmission problems, it's going to be necessary to remove the engine from the chassis to split the cases and perform the necessary repairs, and fortunately removing an engine is fairly easy using readily available hand tools and the steps outlined below, which will show you how to get the motor out of the frame, and into your own engine building box for further disassembly and inspection.
Although taking the engine out of a dirt bike is not technically difficult, and can usually be performed in short order without assistance, it's important to realize that depending upon the motorcycle, an engine can weigh upwards of 80+ lbs so if you feel you may have trouble handling this type of weight, it's advisable that after preparing the engine for removal as outlined below that you seek help lifting the engine out or back into the chassis, otherwise you may find yourself in an uncomfortable situation with pinched fingers.
- First Make Sure the Motorcycle Is Clean
- Before beginning removal of the engine, it's important that everything is clean and our article on washing a dirt bike is an excellent place to begin, as a clean motorcycle will make working on things more enjoyable while minimizing any chances of dirt getting into places it shouldn't, ultimately allowing greater inspection abilities, and a professional end result.
- Drain the Oil(s)
- With a clean motorcycle and before doing anything more, place a drain pan under the bike and remove the oil drain plug(s), as doing this early on will allow the transmission or engine oil to drain while you're preparing the engine to come out of the frame.
If you're planning on disassembling the bottom end, our article on changing the oil in a 2 stroke has some excellent tips for getting the majority of oil out of the gearbox and clutch, as removing as much oil as possible BEFORE you put the engine on the bench for disassembly will greatly lessen any mess on the bench during disassembly.
- Place The Motorcycle On A Service Stand
- Once the oil has finished draining and you reinserted the oil drain plug(s), clean up any residual oil, then place the motorcycle securely on a purpose built motorcycle stand similar to what's pictured above so the rear wheel is elevated, as doing so will relieve the suspension of the engine's weight, and make removal and reinstallation of the swingarm pivot much easier on bikes where the swingarm pivot passes through the back of the engine.
- Remove the Body Work, Gas Tank and Subframe
- With the motorcycle securely positioned on a stand, you can begin removal of the seat, gas tank and radiator shrouds, although be advised that most motocross style bikes have a removable subframe that enables removal of the subframe, air box, side panels and silencer as a whole, allowing quick access to the carburetor, rear shock and rear of the engine, so if you're working on a dirt bike with a removable subframe, leave the side panels and silencer intact and just loosen the intake boot which connects the air box to the carburetor, then remove the 3 bolts securing the subframe, ultimately removing the subframe, airbox, side panels and silencer as an assembly.
- Remove the Carburetor
- Removal of the carburetor from the engine's intake boot will now be possible merely by loosening the clamp and pulling the carburetor from the intake boot with the cable(s), wires and vent hoses attached, but upon removal of the carburetor, be sure to place a cap over the fuel inlet, and carefully wrap the carburetor in a clean rag to prevent contamination while the engine is out, although if the carb appears to have ingested any trash, now would be the time to disassemble and clean the carburetor, otherwise engine damage could result shortly after reassembly from a lean, or contaminated fuel / air mixture.
- Drain the Engine Coolant
- Most modern liquid cooled motorcycles have a coolant drain, often disguised as a cover bolt at a low point in the cooling system, and this bolt usually has an 8 or 10mm head and can be distinguished by being the only one with a copper, or aluminium crush washer between it and the cover, although you may want to review our article on servicing the cooling system for some hazards to be cautious of, as well as some tips that may prove invaluable, and simplify removal of the coolant while minimizing any messes.
- Remove the Radiator(s)
- Removal of the radiator(s) is usually optional, but doing so will minimize any chances of core damage during removal or reinstallation of the engine from the frame, as well as having the radiator(s) and hoses out of your way will give you more room to work with when handling the engine during removal and / or installation.
- Remove the Exhaust
- Removal of the exhaust should be pretty straight forward, and the expansion chamber or head pipe should come off of the bike by simply removing the spring(s) or nuts securing the pipe to the cylinder, and the mount(s) securing the exhaust to the frame. Should your expansion chamber or header have suffered blows in the heat of battle and has some unsightly dents in it, now is the time to have that beat up pipe repaired, as bent up pipes can be sufficiently repaired at a fraction of what a new pipe costs.
- Disconnect Any Electrical Connectors, Cables or Hoses
After removing the carburetor and exhaust, disconnect any remaining electrical connectors, (CDI, Ignition Coil, FI Components) that would prevent removal of the engine from the frame, followed by removing the clutch cable or hydraulic actuator, and securing any coolant or vent hoses so they don't snag or hang up and impede removal of the engine.
- Disconnect the Drive Chain
- Find and carefully remove the master link while paying close attention to the direction of the master link clip as illustrated in our article on servicing the chain and sprockets, then remove the chain from the countershaft sprocket to allow removal of the engine, or alternatively you can leave the chain intact and remove the countershaft sprocket, then remove the sprocket from the chain, leaving the chain resting against the swingarm, allowing removal of the engine without the need to break the chain.
- Remove The Swingarm Pivot
- If the motorcycle being serviced has a swingarm pivot which passes through the back of the engine cases, this will obviously need removed to permit removal of the engine, although if this pivot is frozen and does not come out easily, Do NOT attempt to beat the pivot shaft through to the other side, as there are methods of getting a stuck swingarm pivot out without destroying anything as our article on servicing the rear suspension illustrates.
- Remove the Motor Mounts
- With all the hoses, cables and wires running from the engine to the chassis disconnected and / or secured, remove any engine mounting plates with their accompanying nuts and bolts, followed by removing any remaining motor mount bolts which pass through the engine, then removal of the engine from the frame is fairly straight forward, as at this point it's mostly a matter of lifting and rotating the engine until it is clear of the frame.
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