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Difference between revisions of "Used Motorcycle Evaluation"
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* Batteries are almost always located underneath the seat, though some modern V-twin [[sportbike]]s 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 almost always located underneath the seat, though some modern V-twin [[sportbike]]s 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. As noted below (in [[#ENGINE/FLUIDS/CARBURATORS]]), warm bikes start much easier, so take that into account when making a subjective evaluation of the cranking sound. | * 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. As noted below (in [[#ENGINE/FLUIDS/CARBURATORS]]), warm bikes start much easier, so take that into account when making a subjective evaluation of the cranking sound. | ||
* 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 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. | * 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. | ||