Mike_Thompson Posted October 14, 2005 Share Posted October 14, 2005 Hey guys, Moderators... didn't rightly know where to post this so please forgive me if it's in the wrong area... Does anyone know if there are any hazards to jump starting a motorcycle off a car engine? It sounds like a dumb question, I know, but the bike we're working on has been sitting unused for 18 months. Don't worry, we've already smacked the guy around a bit... We've changed the oil, drained and refilled the gas tank, changed the plugs, etc, etc. We're now trying to get the thing started and we've pretty much drained the battery trying. We've tried jumping the bike by "popping the clutch" but we're running into a dead end (plus I'm getting really tired of hauling the bike up and up and up a hill. Not fun... So... is it possible to jump start a motorcycle off a car battery without frying the electronics or burning out a battery etc? Link to comment
chrisz Posted October 14, 2005 Share Posted October 14, 2005 I've done it twice with my VFR, hook up as usual just don't start the car engine. Let the bike battery take the juice from the car battery without the car engine running. Link to comment
Paul Mihalka Posted October 14, 2005 Share Posted October 14, 2005 Steps to jump-start, same for car or bike: Connect the jumper cables to the two batteries but leave one ground connection off. Start helper car engine. Connect the ground that was still off. Run car engine for at least 10 minutes. You can accelerate the car engine to a fast idle. This will put some charge into the dead battery. Very important: now shut off the car engine. With the jumper cables connected, now start the dead engine. Link to comment
Blake Posted October 14, 2005 Share Posted October 14, 2005 I don't know the "proper" way to do this, but I seem to recall from when I did it years ago that it ended up causing some electrical issues. I can't remember if it was due to excessively jump starting it (i.e. - every weekend cuz I didn't ride during the week), jumping it while the car was still running or what. All I know is that I don't try jump starting from a car anymore and when I push start, the bike is in 2nd gear (I don't know if you're doing that already or not but I figured it couldn't hurt to add the reminder). Either way, good luck! Link to comment
Joe Frickin' Friday Posted October 14, 2005 Share Posted October 14, 2005 Very important: now shut off the car engine. why shut off the car engine before cranking the bike? I've never heard of doing this when jumping car-to-car; the bike runs on the same 12-volt system, so why would you jump it any differently? Link to comment
Paul Mihalka Posted October 14, 2005 Share Posted October 14, 2005 why shut off the car engine before cranking the bike? I've never heard of doing this when jumping car-to-car; the bike runs on the same 12-volt system, so why would you jump it any differently? The way I understand it, with the car engine running you are already up in the 13 to 14 volt range. If suddenly you apply a very high load like a starter motor, it confuses the helper car's charging system that tries to compensate, and may end up with short peaks of 15 or 16 volts. Electronics don't like that. Link to comment
smiller Posted October 14, 2005 Share Posted October 14, 2005 One concern I would have is the relatively small amount of charge current that motorcycle batteries can withstand vs. car batteries. If you connect the two in parallel (as you would when jump starting) and the motorcycle battery is weak, or perhaps has a shorted plate, and the voltage differential is great then a lot of current can flow from the car battery to the motorcycle battery, perhaps more than the motorcycle battery can take with something nasty happening. Jumping car-to-car should be less hazardous because the other car battery, being larger, can withstand a large inrush of current... for example, a 100ah car battery can probably stand 40 amps of charge current for a while, but it would not be a very good idea to supply a 14ah motorcycle battery with a 40-amp charge (to say the least.) That may also be why it is recommended to shut down the car engine, which will lower charging voltage a little which will help reduce the charge rate to the smaller battery. Link to comment
rdsmith3 Posted October 14, 2005 Share Posted October 14, 2005 I don't know the answer to your question, but have you considered the option of recharging the bike battery with a battery tender? Is there someone you can borrow one from for overnight charging? What about using/borrowing a regular car battery charger just for jump starting the bike? Link to comment
EricJRW Posted October 14, 2005 Share Posted October 14, 2005 I don't know the answer to your question, but have you considered the option of recharging the bike battery with a battery tender? Is there someone you can borrow one from for overnight charging? What about using/borrowing a regular car battery charger just for jump starting the bike? That's what I was thinking... Plus, at least on my father's old Honda 350 (we're talking 1970s here), he told me you could not "jump/push start" a bike if the battery was dead. Maybe things have changed since then, but I've always been working on this premise (and have never tried). Is this wrong? Link to comment
Mike_Thompson Posted October 14, 2005 Author Share Posted October 14, 2005 have you considered the option of recharging the bike battery with a battery tender?Oh... we've done that already and drained it once. Then we started to jump it off a hill... I'm thinking that if we can't get it started with all these suggestions, we're going to motivate him to take it in for a tune up. Thanks all! Link to comment
Red Posted October 15, 2005 Share Posted October 15, 2005 The voice of experience from jumping my SO's bike from my pick up is do not start the automobile. It fries fuses and wiring. I don't pretend to understand electricity, but I have been told that the alternators put out too many amps? for the bikes. Like someone else above stated, your auto thinks there's a big demand for electrons and it sends them out. The bikes can't take that much at one time. Link to comment
KDeline Posted October 15, 2005 Share Posted October 15, 2005 From personal experience. Running car engine fried the battery cells, ruining the bike battery. Engine not running, the bike jumped just fine and battery charged normally on the bike after a long ride. Link to comment
Wooster Posted October 15, 2005 Share Posted October 15, 2005 Plus, at least on my father's old Honda 350 (we're talking 1970s here), he told me you could not "jump/push start" a bike if the battery was dead. Maybe things have changed since then, but I've always been working on this premise (and have never tried). Is this wrong? I think premise is wrong. Most dead bike batteries have small electrical charge, just not enough to effectively turn over starter/motor. Push starting is possible, yet has potential problem of leaving you and dead bike further away from home as opposed to kicking & cursing in the comfort of garage. Wooster Link to comment
Bobmws Posted October 16, 2005 Share Posted October 16, 2005 What bike is it? If it has fuel injection and a fuel pump, you most likely do not have enough juice to operate those items when attempting to push start. Use the car battery with the car motor off, as stated previously. Pull the plugs, they may be fuel fouled from your attempts. Oh, the obvious, is the kill switch in the correct run position? Link to comment
Chugger Posted October 16, 2005 Share Posted October 16, 2005 From personal experience. Running car engine fried the battery cells, ruining the bike battery. Engine not running, the bike jumped just fine and battery charged normally on the bike after a long ride. O Yes I fryed my bmw gel that way as well. That's why I now have a Odyssey Battery. Link to comment
waverider Posted October 16, 2005 Share Posted October 16, 2005 I did this last month. Positive & negative to car battery, postive to bike battery negative to bike frame (ground). Leave car off and start bike. Works like a charm. Don't know if starting car would hurt anything or not but it's not needed. Link to comment
allikanbe Posted October 16, 2005 Share Posted October 16, 2005 Why not just buy a new bike battery? it sounds like you will need one anyway? Link to comment
Knappy Posted October 16, 2005 Share Posted October 16, 2005 I know this is not the exact answer to your question. But! 1. If you are not going to purchase a new battery then: a. Charge battery to full(use vom to check voltage). If voltage is not 13+ volts or if voltage is fast dropping off, replace battery. b. Check to see if it has spark(no spark then check that fuse is not open for ignition system). c. Check to see if it has fuel(to combustion chamber). After this long time lots of items could be varnished and plugged. It does not matter that a motorcycle battery is of a different size that a auto battery as long as both have the same voltage. When voltage is equal no current will flow. It you want the auto battery to actually start the motorcycle #6 or larger wire must be used. On some newer autos it is possible to damage the charging system when trying to jump start anything. Be careful. If you are unsure don't do it. Buy a battery and use a external charger. Knappy Link to comment
smiller Posted October 16, 2005 Share Posted October 16, 2005 It does not matter that a motorcycle battery is of a different size that a auto battery as long as both have the same voltage. Except... the two batteries will not be at the same voltage when you are jump starting a weak or dead battery from a fully-charged one. The weak battery will likely be severely discharged or even have a shorted cell if it is getting on in age. In this case connecting a large car battery to a small motorcycle battery can be very hazardous. If you are going to do it at all minimize the amount of time they are connected... and wear eye protection if the battery is exposed. As others have noted, best choice by far is to use an external charger (which will employ all the necessary current-limiting safeguards) when dealing with a motorcycle battery. Link to comment
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