# Mechanics or Bikers!  Ideas...?

**URL:** <https://boards.straightdope.com/t/mechanics-or-bikers-ideas/124601>\
**Category:** Factual Questions\
**Created:** [August 19, 2002, 4:13pm UTC](https://boards.straightdope.com/t/mechanics-or-bikers-ideas/124601 "2002-08-19T16:13:10Z")\
**Posts on this page:** 1\
**Page:** 2

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**Author:** ![bdgr](https://avatars.discourse-cdn.com/v4/letter/b/a87d85/32.png) [@bdgr](https://boards.straightdope.com/u/bdgr)\
**Post date:** [August 22, 2002, 8:23pm UTC](https://boards.straightdope.com/t/mechanics-or-bikers-ideas/124601/21 "2002-08-22T20:23:34Z")

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> [@](#):
>
> \*Originally posted by casdave \*  
> \*\ ***Bdgr**
> 
> Jump starting is usually carried out from a vehicle whose engine is running, if your battery is low there will be a potential for a large charging current to be drawn to it, which would be fine once the connection has been made, but when you are actually applying the clips you often get some sparking and arcing, some electronic modules really do not like this, and some alarm systems will die.  
> Honda, with its HSS system, which has an inbuilt immobiliser, warn that doing this may void the warranty.
> 
> Jump starting from charged battery is ok but not recommended, best to take out the installed battery and replace with a charged one, or at least remove it until the bike is running(but then replacing whilst the bike is ticking over can be a bit amusing unless you have insulated tools to avoid shorting down to chassis. \*\*

On a motorcycle, you never want the car running, as it will increase the voltage that much more, and there really is no need. Bikes, other than Guzzi’s, dont pull enough current on starting to be a problem. So essentially, you are starting from a charged battery rather than another vehicle, evan though that battery is in a car, rather than on the sidewalk.

disconnecting a battery from a running bike to switch them could cause damage, however, becasue some of the more modern voltage regs will cook when you do this. THis is true of many cars as well. I would never do this, unless I was very familiar with the electronics of the bike in question.

Most noise that would be generated by applying the jumper cables to the battery would be obsorbed by it, the dead battery acting as a big filter capacitor, so I doubt it would cause any problems, but my expertise is with older bikes, and YMMV. When I worked as a bike wrench, it was on old brit bikes, harleys, and a few jap bikes, guzzis and beemers, but even so that was a decade ago. My sepcialty was motorcycle electrics, and electronic engineering was my major before I dropped out to become a rock star(that worked out so well for me)…

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