Used Bike Guide – Electrics & Battery

Filed under: Buyers Guide |
  • Check to make sure the headlights (high/low) work. (On some bikes, the headlight won’t come on until the engine does, so you may need to start the engine to test this.) Make sure the turn signals work, make very sure that the oil pressure light comes on when you turn on the ignition, and goes out when the engine starts! Make sure the neutral indicator light works. Make sure the starter works. Make sure the brake levers light up the brake light. Make sure the horn works.
  • Basically, check all the switches as well as the signalling and instrument-cluster lights. (Bulbs are pretty cheap to replace.)
  •  A common way to steal a motorcycle is to hammer a large flat-head screwdriver into the ignition switch, and to start the bike by forcing (breaking) the lock. Check to make sure that the key works, that a wrong key (or screwdriver) doesn’t work (careful not to break it yourself!), and for any possible internal damage. Ignition switches [1] can be a pain to replace, since they (obviously) match the same key profile of the seat release and gas cap release locks. There are some aftermarket units available, but you’re better off going to a dealer to get OEM replacement parts. Probably around £200 + 1.5 hours of labor to replace.
  • If the bike has one*, you should also test to make sure that the sidestand’s engine cut-off is working. These are designed to prevent you from riding off with the sidestand down, taking a left turn, and getting flipped onto the ground. They work in different ways — some prevent the engine from starting when the sidestand is down, some only prevent the engine from running when the sidestand is down and the bike is in gear (i.e., not neutral.) (Still others will let you put the bike in gear while the sidestand is down, simply killing the ignition as soon as you release the clutch, but these are kind of rare.) The design where ignition is killed when the bike is put into gear is a bit more dangerous to test than the design where it won’t let the engine start with the sidestand down. You may want to start by putting the bike in neutral and trying to start the engine (once you know that it actually will start!) with the sidestand down. If it does start, we need to test to see if the safety has been removed or if it’s just the other design… grab the clutch all the way in, hold the front brakes on hard, make sure the sidestand is down, and click the bike into first gear. If the engine dies, the sidestand cut-off switch works. If it continues running, the sidestand cut-off switch has been removed from the circuit. This might mean the bike has been raced, but it’s more of a clue to check elsewhere for evidence of racing, since by itself it doesn’t really mean anything. If the sidestand cut-off switch does not work as designed, you must be very careful (if you buy or test-ride the bike) not to ride off with the sidestand down! Now that we’re done with this test, put the bike back into neutral, release the clutch, and kill the engine.
  • *=Some bikes won’t have such a cutoff. This includes certain Ducati models and a wide variety of older bikes. As noted above, if you buy a bike without a (working) sidestand cutoff, you’ll need to be very careful to avoid riding off with the sidestand down.
  • Make sure the kill switch on the right handgrip stops the engine when it’s running. (Dirt bikes will have a kill button on the left handgrip.)
  • Batteries are almost always located underneath the seat, though some modern V-twin sportbikes locate it beside the engine, and many dirt bikes and older standard bikes locate it behind a plastic side cover below (or below and slightly behind) the seat.
  • Batteries are very hard to test without the appropriate tools, and even then they’re kind of mysterious and unpredictable. For our purposes, if the battery starts the bike, it’s good. If it doesn’t, £50 to replace. Without hearing “good” batteries, it’s hard to tell what “good” sounds like, but if the starter’s cranking is obviously weak, that’s probably a good indication that the battery is too.
  • If the bike doesn’t have an electric starter (i.e., it’s a kick-start), there’s no good way to test the battery without examining the lead plates for white sulfide deposits (bad) and checking the specific gravity of the acid with a battery hydrometer. Most auto parts places should carry those; just make sure you get one with a long, thin tube, since most cage (“car”) battery hydrometers are too large to fit into bike batteries. On the other hand, if your bike is a kick-start, it doesn’t depend on the battery too much, and checking it is less important.
  • If the headlight gets brighter as the engine revs, the battery could be discharged (or dead), though it’s probably more likely that the voltage regulator is toast. £80-120 for a new one, plus half an hour of labor to install. Don’t compare brightness at idle to brightness at 10,000 rpm… compare ~2,500 rpm to ~7,000 rpm.) It’s hard to diagnose this problem by headlight brightness alone, but for starters, try charging the battery and repeating the test, or, if that doesn’t work, replacing the battery and repeating the test. If it’s still getting brighter as revs go up, try testing voltage across the battery at ~3,000 rpm… should be 13.8v or so. Less than 13.2 (or more than 14.4) and you probably have a bad stator (~£300 for a new one, ~£150 to get the old one rewound) or a bad regulator (prices as noted above.) This probably sounds pretty involved, and it probably is, if you don’t know what you’re doing. You may want to look for a bike that won’t require as much work… taking the bike to a mechanic for a professional diagnosis will cost you £50-£100 or so, but will help you make that decision. If you have your heart set on this bike, it’s probably worth it; otherwise, it probably isn’t.