2 Stroke engine repair can be accomplished once the severity of the problem or damage is assesed. As with all engines, they require two basic things to operate. First all engines require fuel. There are a few ways to check if the engine is getting fuel. Remove the spark plug and see if they are wet. If the spark plug is not wet, you can remove the float bowl to see if fuel is being delivered to it. If there is no fuel you can check the needle and seat of the carburetor, or the fuel pump. You can generally repair a sticking needle simply by moving the needle manually. If the 2 stroke engine is fuel injected you will need a fuel pressure gauge and will then need to attach it to the fuel rail. Check that the specified pressure is being reached. If not, the fuel pump is probably faulty. The next important thing to check is that the engine is producing spark.
Remove the spark plugs and lay them on the engine and use the pull start or turn the key to spin the engine over. The spark plugs should be sparking. If there is no spark make sure that the coils are grounded. Also check that 12 volts are passing through the ignition switch and powering up the coils. If there is no battery or even if there is, the stator coil could be not charging or may have a short. If there is power at the coil but the spark plug won’t spark, the coil may be bad. On fuel injected engines a bad crankshaft position sensor may cause the coils to not fire also. If your engine will not spin over, first check the battery to see that it has 12 or more volts,assuming it has a battery. Many 2 stroke engines also use a recoil pull start, make sure the recoil is working properly. If the 2 stroke engine will still not rotate, once again remove the spark plugs. If the engine won’t rotate, there may be a mechanical problem.
It is possible the 2 stroke may have a stuck piston and need a rebuild to be repaired. If the piston is damaged you may see aluminum spots on the spark plug. In lesser piston “sticks” you will need a flashlight to look through the spark plug hole to see if there are lines running vertically in the cylinder. If there are lines in the cylinder bore the cylinder “jug” will need to be removed. First the aluminum will need to be removed by a solution of muriatic or pool acid. This will eat away the aluminum so that you can see the damage. If the damage is minimal the cylinder can be honed out slightly to repair the wear marks. The 2 stroke piston will need to be replaced and the piston may need to be slightly larger depending on how much cylinder material has been removed. Always make sure that the piston ring pin is not in line with the exhaust port of the engine. Most 2 stroke engine pistons have an arrow that points to the exhaust side of the engine. Do not place the piston in backwards or the ring will expand out into the exhaust port causing severe damage. In a serious damaged cylinder the repair can only be done by removing the cylinder sleeve and replacing it with a new one. These are the general problems that can happen or repairs needed on a 2 stroke engine.