scooter valve adjustment

For any scooter engine to work properly, both the intake and exhaust valves must open in time. The rocker arms are responsible for opening the valves. At the end of a scooter rocker is the tappet. With wear and tear, cleats become out of adjustment and must be readjusted periodically. The recommended setting varies from brand to brand and it is recommended to consult the service manual for the specific type of scooter.

Valve lash, also known as tappet lash, will have a direct effect on engine performance. Valve clearance is the distance in minutes between the tappet and the corresponding valve stem. It is critical that this clearance be within specifications (specified by the particular scooter brand) for the scooter to function. Valves that get out of adjustment over time can cause loss of compression, reduced power and engine damage. In some cases, your scooter may not even start.

With regular use, you should incorporate valve adjustment as part of your regular maintenance schedule. This should be done in accordance with any manufacturer’s recommendations, which can usually be found in the documentation that came with your particular brand of scooter.

Before you begin, one of the first things that is recommended is that you have the right tools for the job. While you can get away with using some very “basic” tools, it’s always recommended that you definitely get tools that are specific to the job. For example, while you could make cleat adjustments with a 9mm wrench and a pair of needle nose pliers (which I’ve seen them do), you would achieve easier and more accurate results with a cleat adjustment tool. At the time of this writing, a decent tappet setting tool was going for about thirty bucks online. If this sounds like a lot, remember, as you incorporate valve adjustment into your regular maintenance schedule, you may find that the cost of the tool broken down across many jobs makes the expense really small.

For this job, you should have a feeler gauge set and a tappet setting tool. Also, if you don’t have the tappet setting tool, you can use a 9mm wrench and a pair of needle nose pliers. You absolutely need the feeler gauge set to get the proper clearance.

Start with the engine of your COLD scooter. The reason you want the engine to cool is because as the engine heats up the metal expands. This expansion will surely make the headroom bigger once the engine cools down. This would result in too great a valve lash which would probably not allow the valve to open properly. Place the scooter on the center stand so that the rear wheel is off the ground. Remove the valve cover and place the screws in a small container so they don’t get lost. There will be two valves. One is the intake valve and the other is the exhaust valve.

Next, turn the engine fan until it reaches “Top Dead Center”, which is when the piston is at the top of its compression stroke. The top dead center mark is stamped on the flywheel and is usually indicated as a “T”. At this point, both valves should be fully closed and the valve clearance between the rocker arm and the valve stem should be at its maximum. Both rocker arms will be at minimum height positions on the camshaft lobes. In addition to the marking on the flywheel, and/or there are also markings on the outside of the cam sprocket that can also be used.

Once at top dead center, loosen the lock nut. To adjust the clearance, use a feeler gauge set. You should be able to slide the correct size gauge (per the manufacturer’s specifications) between the tappet and the top of the valve stem with minimal resistance. Similarly, if you can freely pass the pressure gauge, the clearance is too large. Once you have established the correct clearance, tighten the locknut and recheck it. Now do the same again for the other valve. Again, the recommended setting varies from brand to brand and it is recommended to consult the service manual for the specific type of scooter.