After this engine sat for awhile it wouldn’t restart. This is a 2 horsepower briggs and stratton engine. This engine is on a rototiller, but the problem would be the same with any other engine. The first thing to do is to decide if the problem is fuel or spark related. These are the first problems to check for. First check the obvious thing like adding fresh gas to the tank. Generally if the problem is fuel related the engine will at least sputter. Another way to test this is to remove the spark plug and squirt a small amount of gas in the cylinder, replace plug. If the engine starts but doesn’t stay running you have a carb or fuel issue. If it still does nothing you should remove the spark plug and lay it on the cylinder head. Then you probably have no spark and have an ignition problem.
If you have a lawnmower that is backfiring or pulling the pull start out of your hand, the flywheel key may be sheared. The key in a small engine mates the flywheel to the crankshaft in a certain spot. The flywheel can only fit one way or the timing will be incorrect. The flywheel key can be sheared if a heavy object was hit by the mower, such as a rock. With no key keeping the engine in the right place it will no longer run correctly.
Small engines can be purchased for many self hobby types. Places like Northern Tool are great for small engines anywhere between one horsepower to 23 horsepower engines. These engines are purchased for many projects like water pumps, go carts, homemade generators, log splitters and various other projects. Pay attention to your project before purchasing an engine. Some projects require verticle shaft engines where others need horizontal shaft engines. The engine configuration generally will not interchange with the others. You will probably need accessories also to couple the engine to whatever drive system you use. Generally the same store, such as Northern Tools, will have sprockets, and drive shaft coupling parts to connect to whatever parts and components that need to be driven. If you plan to make a go cart briggs and stratton and tecumseh both have race cart series. It would make sense to use the same engine so that you have all the same aftermarket parts available to you. If you plan to build a generator make sure the engine has a good governing system to control the engine rpms. A generator engine should be run around 3600 rpms to keep the cycles at 60 hertz as regular ac power.
Recoil rope broke on your small engine? Here is a guide to repairing a lawnmower, chainsaw, outboard motor, snowmobile or weed eater recoil. The pull start assembly is usually easy to get to and will not take long to repair. Generally there are up to four screws that will need to be removed for the recoil assembly to come off. Once the housing is off you will see that the rope knot is probably still tied inside the inner housing. To make things easy try to pull the string through the hole of the recoil where it previously or still passes through. pull the rope and count how many times it turns. If you were lucky, that may be how many rotations you will need and won’t have to wind the new rope more turns. When the rope is tight see if you can stick a screwdriver all the way through the recoil slots so it won’t unwind. Slowly release the rope and make sure it won’t unwind. Carefully untie the recoil rope knot located close to center of the recoil and inline with the hole the rope passes through. When replacing the rope only use a rope made for recoils. A new general purpose recoil rope is literally only a few dollars.
Small engine timing is completely mechanical. The coil is mounted closely to the flywheel. The flywheel is the large circle with cooling fins. The flywheel is on the opposite side of the engine from the output shaft. The flywheel has magnets mounted in it. As the flywheel magnets pass the coil they induce a current. The coil then discharges to the spark plug. The relationship of where the coil sits and where the flywheel magnets are, dictates the timing. The coil can be moved slightly to change the timing. Move the coil in the direction the flywheel moves and the timing will be retarded and opposite to advance timing. The only other factor that affects the timing is the flywheel. Occasionally the flywheel can shear it’s key on the crankshaft. The key locates the flywheel in the correct rotational spot to insure correct timing. If the key is sheared the timing can be anywhere, and the engine may spark but not run. The key is square and can be viewed from the end of the shaft. The key will have a cutout in the shaft and the flywheel. Offset keys purposely rotate the flywheel to advance timing.
Small engines are very touchy with their tuning. EPA regulations have made small engines run much leaner than they have had to in the past. This will make the engines run cleaner and be more fuel efficient, but generally don’t run as well. Also if the carburetor has any build up in it the engine will be too lean and will surge. To compound the problem most new carburetors are non adjustable due to EPA regulations. Most small engine carbs have a high speed and low speed circuit to control the fuel. When you hear an lawn related engine surging it is almost always lean. If the engine is older, the carb screws on it’s side may be adjustable. You need to locate the main circuit or high speed screw that usually has the letter H along side it. This screw is a fuel control screw that will have a spring under it. As you turn the screw out it delivers more fuel to the engine. Don’t turn the screw more than 1/8 of a turn at a time then wait a few minutes before changing again. The engine should smooth out and the setting should stay there.