Service

SERVICE

Battery Bandits

I own a 1979 Yamaha 650 Special and am at my wit’s end trying to find the cause of a constant battery drain that has been going on for two years.

It started in June of 1991 when I installed a new battery because the existing one wouldn’t take a charge. Two months later, the bike was becoming hard to start because of low battery voltage, even when kick-starting. By April of 1992, I had to have another new battery installed because the previous one kept going dead and wouldn’t hold a charge. Less than a month after that, the battery started losing its charge again, so I had my dealer check the entire electrical system and tune the engine. Everything worked well for a few days, then the battery started draining again. A month later, my dealer installed a rebuilt stator (no new ones were available), and the bike worked fine for a few days until the battery started draining again.

Since then, I’ve just charged the battery a lot, but now it won’t take a charge. My dealer and my husband have tried everything they can think of to fix this problem. Can you help?

Margaret Lambrinides

Waldwick, New Jersey

Three significant points: 1) You did not specify whether the battery drains as the bike is being ridden or while parked; b) you ’ll need a volt-ampohm meter to diagnose some electrical components; and c) the space limitations of this department do not allow a thorough, detailed diagnosis of your electrical problem. But let ’s give it a shot anyway.

If your battery drains while you ’re riding the bike, you have to determine if charging current is reaching the battery. To do that, locate the fusebox under the seat and find the red wire that leads into it. Start the engine, then disconnect the fusebox and connect the positive (red) wire of the voltmeter to the end of the red fusebox wire that leads to the voltage regulator (it’s the end that does not lead to the battery), and connect the negative (black) wire of the meter to the ground (negative) terminal of the battery. Rev the engine to about 2500 rpm and check the voltage output, which should be between 14.5 and 15 volts DC. If it is, your problem is not in the charging system and the battery should charge properly as the bike is ridden.

If the voltage is below those limits, your problem is most likely either in the voltage regulator or the rectifier (considering that you’ve already replaced the stator). Rather than trying to explain the multiple-step procedures for diagnosing the regulator and rectifier, we instead recommend you buy a shop manual for your bike and follow the instructions in the Charging System Troubleshooting section.

If your battery drains while the bike is sitting, the volt-amp-ohm meter can help you trace the cause. First, install a fully charged battery in the bike but leave the ground wire disconnected. Connect the positive wire of the meter to the negative terminal of the battery, and clip the negative wire of the tester to the battery’s ground wire. With the ignition in the Off position and no electrical components in use, the ammeter ought to read zero at all of the various ampere settings on the meter.

If the meter shows any reading whatsoever, start disconnecting the bike ’s electrical components, one by one, until you unplug one that causes the reading to drop to zero. When that happens, you will have found the source of the battery drain.

Plug check

When hundreds, probably thousands, of motorcycle and auto buffs read their owner’s or shop manuals, they invariably encounter confusing advice to use colder sparkplugs for “high speed” riding. The problem is that everyone seems to have a different or vague conception of what constitutes high speed. One would think that factors like engine temperature, high rpm, lugging or octane rating would be more relevant to plug heatrange selection.

On trips, my ’84 Gold Wing Interstate usually is run between 55-70 mph for long periods in hot weather. I use NGK DPR8EA-9 plugs in the winter and DPR9EA-9 in the summer. The area around here is mountainous and often requires long, fourthand fifth-gear uphill running. The colder plugs seem okay, but I don’t know if they are necessary. By contrast, when I used colder plugs in older Harleys and Indians, in cool weather they would cause the engine to cough and hesitate during acceleration.

Harold Lonsdale Tillson, New York

More than anything else, sparkplug heat range is based on combustionchamber temperatures. Any factors that raise temperatures in the combustion chamber-whether it’s lugging or high rpm or “high-speed” riding or numerous others-are potential reasons to require colder sparkplugs, while factors that lower those temperatures could call for hotter plugs.

Sparkplugs come in different heat ranges so they can be matched to any given engine’s range of combustionchamber temperatures. A plug’s heat range is determined primarily by the length of the porcelain insulator that surrounds its center electrode. Hot plugs have longer insulators to retain more of the heat of combustion, while cold plugs use shorter insulators that retain less combustion heat.

The use of plugs with the correct heat range is necessary to keep the plug from either fouling or overheating. A plug fouls when the insulator remains too cool to burn off certain by-products of combustion that conduct electricity. Once those deposits collect on the insulator, they shortcircuit the plug and prevent it from firing. Conversely, a plug overheats when its insulator runs too hot, which can ignite the incoming fuel mixture before the spark can ignite it-a classic case of preignition.

Generally, the proper plug for any engine is the coldest one that will not foul or cause misfiring under normal riding conditions.

Flood watch

I’m having a problem with my 1983 Honda V65 Magna. After I start it up, it runs fine for about 10 seconds, then floods out and kills the engine. If I quickly turn the fuel petcock off just as the flooding begins, the engine will clear out and run normally until it runs out of gas.

I bought this bike used in December from someone who had neglected it. Everything was all gummed up when I got it, but extensive work cleaning the carbs, the brake system and other TLC has made it run nicely with the exception of this flooding problem.

The fuel pump appears to be working normally and is not equipped with a pressure-relief valve. I checked the fuel cutout relay according to the Clymer manual and it failed the test, so I replaced it. But the new relay failed, too. I’ve now spent $45 on a relay I didn’t need and the flooding problem still exists. Any help Cycle World could give me would be greatly appreciated.

Arthur G. DeJager Smithville Flats, New York

Your V65 is equipped with a fuel pump because its gas tank is located beneath the seat, which is lower than the carburetors. But there’s a simple way to determine if the pump is the problem: Temporarily eliminate it. Unplug the fuel pump’s electrical connections and disconnect the main fuel line between the pump and the carburetors. Then find a small, clean container big enough to hold at least a quart of gasoline—a gas tank from a lawn mower, for example-and hang it from the Magna’s handlebar so it’s higher than all four carburetors. With a little improvisation and a short piece of fuel line, you should be able to connect the container to the bike ’s main fuel-inlet junction.

Then, just start the engine and see if the engine still floods. If it does, the problem is that either the floats in two or three of the carburetors are sticking open, or that two or three of the needles are not sealing adequately (flooding in two or three cylinders would be sufficient to kill the engine). If the engine does not flood, the problem is with your fuel pump, which is delivering excessive line pressure and overpowering the float needles. □