What could be wrong if a Yamaha PW80 will not start?

Answer 1

Three simple things to check !There are three things needed for your PW80 to run, They are: 1) Spark, to ignite the fuel air mixture in the combustion chamber. 2) Fuel, this must be present in the caruretor to be mixed with air to be sucked into the combustion chamber. 3) Mechanical compression of the fuel air mixture. If any one of these three elements is missing your bike won't run. First, check for spark, pull the spark plug and hook the plug wire up to it and then touch the business end of the plug to an unpainted surface on the motor, then kick over the bike, there should be a nice fat blueish spark. If there is no spark try this test with a known good plug or a new one. If still no spark, check the wire and check the coil. Check to make sure any wire connectors aren't corroded, it's easy to clean them with a bit of emery cloth, or try WD40 Next, is the gas turned on, and does it have enough fuel? Take the air breather off so you can see into the throat of the carburator, you may need a small mirror. Turn the throttle sharply while looking into the Carb throat, you should see a squirt of fuel being shot into the carb body. If you do not see the fuel, then you must check to see that the carb is getting fuel, if it is getting gas, it may be old gas, I always replace the gas and the spark plugs if the bike hasn't run for a while. The third thing to check is to see if you have good compression. With the spark plug out of the engine, put you thumb or finger over the spark plug hole and crank over the engine. If your thumb gets pushed off the hole in little spurts, then there is a good chance that the compression is OK. Now, be aware that for a bike to run all three of these things must happen in a very precise and controlled manner. But, if the bike was running before and has just been sittting for quite some time then replace the fuel and the spark plug and try it again. It probably wouldn't hurt to give the carb a bath with some carb cleaner either.