Trouble Shooting
TROUBLE SHOOTING
Roadside Remedies For Motorcycle Malfunction
I HATE to see a motorcyclist in trouble, so I pulled over on the shoulder and parked. One look made me wish I hadn't. The small Twin appeared to have disintegrated. The plugs were out; and the magneto inspection cover was off; the carburetor and air cleaner had been stripped to the last tiny washer-and thoughtfully laid out on a patch of gravel; and assorted wires hung like dead spaghetti. The proud owner and his attractive passenger grinned engagingly at me-freckles and oil.
STUART MUNRO
"Know something about these?" he asked.
"A little," I said guardedly. "What happened?"
"I dunno-it just quit. Just like that. Right, Donna?" Donna nodded vigorously, prettily.
"Just like what-did it spit or sputter, or just cut dead, or what?"
"Well, like-uh-no go. Just cut and like that."
Communication was not his strong suit, but 1 felt he could always get a job writing manuals for imported motorcycles. I cleaned and carefully assembled the carburetor and air cleaner, switched on the gas and it gurgled happily. Brushed and gapped the plugs, ran some paper between the points and replaced the magneto cover. I tested the plugs for fire and found big, fat, blue ones; put them back and connected all the loose ends. "Try it," I said cautiously.
It fired on the second kick and crackled merrily.
"Thanks," he shouted over his shoulder. "Swell. What did you do?" And they were gone. What did I do? I'll never know
Fixing a street machine that quits or won't start is not complex and shouldn't throw anyone. The main thing is to maintain a logical sequence and keep your cool. Generally, if it cuts dead suddenly, it's ignition trouble; and if it dies and picks up, and dies again you have fuel problems. It can only be in the ignition or in the fuel system-and even if you're not John Dunn, an ounce of common sense can fix the majority of roadside annoyances. So next time it won't start, and you've only got 10 minutes to meet that new one with the green eyes-relax. To quote IBM, "THINK!" After the sixth prod without a cough-STOP. You're just wasting energy.
DIAGNOSIS: Remove the plug(s) and make a mental note of the condition—wet or dry? Connect the plug lead and lay the threaded part of the plug against the cylinder fins, AWAY from the plug hole. Still holding it there, kick the engine over and watch for a blue spark jumping between the electrodes. If there is no spark, you have ignition failure; but a good spark means probable fuel troubles-and this certainly is the case if the plug was dry when you removed it.
FUEL: The symptoms are good spark and a dry plug.
You could just be out of gas. Check the tank, and if it's low, lean the bike to the side the gas tap is on. An extra five miles may be available this way, repeating the process every mile or so, and coasting where possible. Don't forget to check for a plugged vent in the gas cap. This can cut off your gas like a tap.
If this checks out, then the stoppage is elsewhere—between the tank and the cylinder. So cut your troubles in half by going to the float chamber. If this is dry, inspect the carburetor fuel filter and clean it if necessary. Test if gas comes out of the feed to the carburetor, then check the tap; finally make sure there's no rust or sediment in the tank.
A full float chamber usually means blocked jets. Remove them and blow them out-don't use wire. Water can obstruct a jet as surely as dirt. What happens is that the water droplets are too large to go through the orifice so the gas is cut off. Shake out the float chamber and the jet sump into the palm of your hand. The gas will evaporate and leave little globules of water. Clean and dry the carburetor-and find out where the water came from.
Still no go? There is a possibility that your carburetor settings are out of adjustment. Adjust as closely as you can to the manufacturer's recommendations, and try starting by run and bump. Once you've got it going, adjust the slow-running setting and reset when the motor reaches operating temperatures.
Finally inspect the body of the carburetor for cracks or other damage. This should be quite evident by leaking gas, and a temporary repair can be made with chewing gum.
MECHANICAL: The symptoms are good spark, and a wet plug.
There is a possibility that your ignition timing is out, but in the case of a sudden failure this is unlikely. Ignition timing problems show themselves usually by spitting back at you through the carburetor, or by erratic banging in the exhaust system. If you suspect your timing is out, re-time to the settings detailed in your manual.
When the plug is wet, there must be a flow of fuel to the combustion chamber-but you could be getting too much gas. Inspect the carburetor for evidence of flooding, which will be apparent by dripping gas. Dirt can prevent the float needle from seating, so causing a continual flow of gas; the float could be punctured having the same effect; and I have known jets to drop out. A get-home tip for a punctured float is to heat it gently. The expanding air will force out the gas, and should last you home.
If the carburetor is not flooding and your timing is accurate, test the compression by standing on the kickstart with the plug in. A loss of compression can be caused by a number of faults, but the most likely is a blown head gasket. Inspect the cylinder head joint for oil leaks. On four-stroke engines, difficult starting may be caused by a tight valve clearance, resulting in the valves remaining open for the entire cycle. Lastly, and I hate to mention it-you could have broken piston rings.
IGNITION: Many of my friends, who will cheerfully undertake a major overhaul, go into a cataleptic trance at the suspicion of ignition problems. So, I might add, do I. But in these days of reliable electrical components there is little likelihood of a major breakdown. Most failures can be fixed up on the spot. Let's see if we can simplify the system.
Discussion of electrical faults is always a generalization, because wiring circuits vary on almost every make of motorcycle manufactured. However, most systems have a magneto, alternator or generator which supplies current to an automatic voltage control unit or rectifier. The latter controls the flow of current to the battery, and from there the low voltage current goes through the coil to the contact breaker. The contact breaker grounds this current, causing electrical impulses in the coil, thus converting the low voltage current to the high voltage juice required at the spark plug. That didn't hurt a bit, did it? Now let's see what is most likely to go wrong. The symptoms are no spark, and a wet plug.
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The first thing I do is install a clean, tested and correctly gapped plug. Try again for a spark, and if there is none, I can again halve the troubles by going to the contact breaker points. With the ignition on, flick the points with a feeler gauge-you should see a spark here. Assuming there is life at the points, the trouble must be between here and the plug. Check the high voltage lead at each end, looking for signs of poor connections, dirt or condensation, or cracks in the casing. Clean out the pick-up socket, and inspect the coil wire connections. On magneto ignition insure the high voltage pick-up brush is clean and free to move in the socket.
If there is no spark at the contact breaker points, check the battery first. This should be done with a hydrometer, but the lights and horn give a fair indication. Make sure the terminals are clean and are making positive connections. If the battery is flat, try starting with a run and bump; but get a charge as soon as possible. Assuming the battery is good, check the contact breaker points and gap. Continual deterioration of points means you need a new condenser. Inspect the entire assembly for dampness, water or excess grease; look for a lack of grease on the contact breaker pivot that could be causing stiffness; check the spring to make sure it's not broken; and if all else fails-examine the automatic advance and retard mechanism. Now we start the men-from-the-boys sorting process, and from here on down it's uphill all the way. Very quickly, before it becomes embarrassing, inspect the fuse-if you have one. If it's blown, a piece of aluminum foil wrapped round it can get you home, but get an expert to find out why it failed.
There are only two possibilities remaining-wiring, and the major components. Check all your wiring for cracks or breaks and inspect every terminal, tag and snap connector. But stick to a logical sequence and, by now, you should know where you start and where you go to. If you can't fault the wiring, then you must have a magneto, coil, rectifier or condenser failure. A condenser is cheap and is no trouble to carry. As I said, the chances of complete failure of a prime unit are remote.
Finally, a word to the two-stroke owner. Always suspect your plug in the event of electrical failure. "Whiskering" may be invisible to the naked eye, but is a prime cause of plug-shorting if you use gas with a high lead content. Oil fouling also is common in this type of engine, and if you mix gas and oil, always drain the carburetor when you shut down. Switch off the gas and run the engine dry. Mix precise gas/oil quantities by adding the exact amount of oil to half the gas; agitate thoroughly; add the rest of the gas, and MIX AGAIN-THOROUGHLY. Attention to these basics will eliminate the majority of two-stroke problems. ■
