1. Set the piston of the first cylinder to top dead center (TDC) of the compression stroke. You can do this by removing the spark plug from the first cylinder and inserting a long screwdriver or rod into the spark plug hole. Turn the crankshaft until the piston is at its highest point and the screwdriver is at its highest point.
2. Locate the timing marks on the engine. The GA15 has two timing marks: one on the crankshaft and one on the camshaft. The crankshaft timing mark is located on the front of the engine, just below the water pump. The camshaft timing mark is located on the back of the engine, just above the distributor.
3. Align the timing marks. The crankshaft timing mark should be aligned with the "0" mark on the timing belt cover. The camshaft timing mark should be aligned with the "UP" mark on the timing belt cover.
4. Install the timing belt. wrap the timing belt around the crankshaft, camshaft, and water pump pulleys, and tension it according to the manufacturer's instructions.
5. Start the engine and verify the timing. If the timing is set correctly, the engine will start and run smoothly.
