Diagnosing mechanical problems is relatively simple if you use orderly procedures and keep a few basic principles in mind.
These troubleshooting procedures analyze typical symptoms, and show logical methods of isolating causes. These are not the only methods. There may be several ways to solve a problem, but only a systematic, methodical approach can guarantee success.
Never assume anything. Do not overlook the obvious. If you are riding along and the bike suddenly quits, check the easiest, most accessible problem spots first. Is there gasoline in the tank? Is the shutoff valve in the ON or RESERVE position? Has a spark plug wire fallen off? Check ignition switch. Sometimes the weight of keys on a key ring may turn the ignition off suddenly.
If nothing obvious turns up in a cursory check, look a little further. Learning to recognize and describe symptoms will make repairs easier for you or a mechanic at the shop. Describe problems accurately and fully. Saying that “it won’t run” isn’t the same as saying “it quit on the highway at high speed and wouldn’t start,” or that “it sat in my garage for three months and then wouldn’t start.”
Gather as many symptoms together as possible to aid in diagnosis. Note whether the engine lost power gradually or all at once, what color smoke (if any) came from she exhaust, and so on. Remember that the more complicated a machine is, the easier is to troubleshoot because symptoms point to specific problems.
After the symptoms are defined, areas, which could cause the problems, are tested and analyzed. Guessing at the cause of a problem may provide the solution, but it can easily lead is frustration, wasted time, and a series of expensive, unnecessary part replacements.
You do not need fancy equipment or complicated test gear to determine whether repairs can be attempted at home. A few simple checks could save a large repair bill and time lost while the bike sits in a dealer’s service department. On the other hand, be realistic and do not attempt repairs beyond your abilities. Service departments tend to charge heavily for putting together a disassembled engine that may have been abused. Some won’t even take on such a job — so use common sense, don’t get in over your head.
An engine needs three basics to run properly: correct gas/air mixture, compression, and a spark at the right time. If one or more are missing, the engine won’t run.
The electrical system is the weakest link of the three basics. More problems result from electrical breakdowns than from any other source. Keep that in mind before you begin tampering with carburetor adjustments and the like.
If a bike has been sitting for any length of time and refuses so start, check the battery for a charged condition first, and then look so she gasoline delivery system. This includes the tank, fuel shutoff valve, lines, and the carburetors. Rust may have formed in the tank, obstructing fuel flow. Gasoline deposits may have gummed up carburetor jets and air passages. Gasoline tends so lose its potency after standing for long periods. Condensation may contaminate it with water. Drain old gas and try starting with a fresh tankful.
When she bike is difficult to start or won’t start at all, is does not help to grind away at the starter or kick the tires. Check for obvious problems even before getting out your tools. Go down the following list step-by-step. Do each one; you may be embarrassed to find your kill switch off, but that is better than wearing out your leg. If the bike still will not start, refer so the appropriate troubleshooting procedures.
1. Is there fuel in the tank? Do not trust the fuel gauge. Remove the filler cap and rock the bike; listen for fuel sloshing around.
Do not use as open flame to check in the tank. A serious explosion is certain to result.
2. Is the fuel tap in the ON position? Turn it to RES to be sure you get the last remaining gas.
3. Is the engine stop switch in the ON position?
4. Are spark plug wires on tight?
5. Is the engine start lever in the right position? Is should be pulled up for a cold engine and down for a warm engine.
6. Is the battery dead? Check it with a hydrometer.
7. Has the main fuse blown? Replace it with a good one.
An additional guide that was intended for Mopeds is also very appropriate for any 2-stroke and can be found here. Fred’s Guide