# Physics and the Motorcycle



## A. E. Lowan (Jun 20, 2013)

Question for the bikers out there...

Working on a scene where a character comes running across a parking lot and jumps on his Harley, starting basically as he lets gravity carry him down. Then it occurred to me - I have no idea if this would even work. Help! He needs to get the bike started fast, and go tearing out of the parking lot with security guards chasing him. How does he do it? He's riding a Harley Davidson 1986 Sportster 1100, if that makes a difference.


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## CupofJoe (Jun 20, 2013)

My active knowledge of bikes was a old Royal Enfield 350 but I think the H-D has an electric start, so I don't think he could kick start it as he jumped on. And unless American bikes are very different to the ones I know here, he's still going to need to put the key in to unlock the steering...
With my old RE it would take about 20 minutes to adjust fuel and check points before checking the battery and trying to kick it over. It wasn't transport, it was meditation...


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## A. E. Lowan (Jun 20, 2013)

Well, I was thinking about it after I posted, and remembered that this character has some small magical ability which he usually uses to trip slot machines into paying out, so some mechanical manipulation.  I figure he's well enough acquainted with the mechanics of his own bike to trip the ignition on the move, but what needs to happen with the clutch?  It is in the handle, or the pedal?  I had a very small motorcycle when I was a kid, and I remember it was kick started, but those memories are a bit murky. lol


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## C Hollis (Jun 20, 2013)

The clutch is the lever on the left hand, brake (and throttle) right hand.
Gear shifter left foot, rear brake right foot.

Most bikers leave their bikes in gear when they park them, and even that old Harley will not start, in gear, with the kickstand down.

Chain of events (1):
jump on bike
ignition on
bump the shifter up into neutral
start bike
kickstand up
launch

Chain of events (2)
jump on bike
ignition on
clutch in
kickstand up (will start in gear with kickstand up...as long as you hold the clutch in)
start bike
launch

chain of events (3) (lets assume bike is in neutral):
jump on bike
ignition on
start bike
kickstand up
launch

Also keep in mind that some of these things can be done simultaneously since a couple of steps are done with the left foot, such as kickstand up and ignition on.

Just an example of how I launch on my bike, when I'm not being chased down (I typically fumble one of the steps and get caught when I am being chased):

I'll walk up to the bike and bump the heal shifter down to put it in neutral.  While I'm swinging a short leg over the seat, I'll turn the bike on.  Then it's hand on break, start it with my thumb, kickstand up, all in one fluid super cool motion that causes me to wink at myself in the right hand mirror, cause, well, you know...

Sorry.

Then it's pull in the clutch, kick it down into first and launch.


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## A. E. Lowan (Jun 20, 2013)

OMG Thank you SO much!  That is super helpful!


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## ThinkerX (Jun 20, 2013)

It's been decades since a bum knee ended my motorcycle riding.  Never had a harley; a bit impractical up here back then.  What I did have was a succession of street legal dirt bikes.

With some of them, your scenario could almost work IF the bike was in neutral upon being started AND the bike was well tuned to start with.  Lessee...

Jump on bike, pull clutch with left hand while at same time turning key with right hand and bringing right foot down on kickstart a tenth of a second later.  Then release clutch and apply throttle.  Do this overfast with the kind of bikes I used to ride, and you'd be doing a wheelie at take off - front tire a couple feet in the air.  We used to have contests to see who could keep the wheelie going the longest.  Best I managed was a couple hundred yards.


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## Quillstine (Nov 12, 2013)

*Rolling Start*

So I know this thread is older and the scene is probably long since written and gone, still I had a suggestion I thought I would add! 
What I think would be cool, if I was being chased at least, is this. The Sportsman 1100 has a rear folding kick stand, most newer bikes do, so you can “drag” them of the stand. The forward motion of the bike will flip the stand up and out of the way.
If your character is running, he could jump onto the bike from its rear, press in the clutch and start pushing, straddling the bike if you will. The stand would come up and away on its own. If he magically manipulated the ignition on (or just fumbled with the key as he pushed) and he was “pushing” the bike forward and about a slow jog, all he would need to do is let the clutch out.
In short, the rear wheel would drive the chain, the chain once the clutch was let go, would drive the engine and it would simple start to run. The starter would never need to be touched.
Of course, on a really technical note, he would need to have parked in 2nd gear, or more likely 3rd, in first the “leverage”, if you will, would be to great and the rear wheel would simply lock up. If by chance is motor was a little worn, and the compressions where down, it might be possible to get it going in first from a rolling start. But the bike would most likely jump out of his hands…yes I am speaking from experience there! In 3rd the engine splutters up to speed, nice and smooth!
Perhaps this is the easiest way to explain it!
Starting A Motorcycle With A Dead Battery - YouTube


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## A. E. Lowan (Nov 12, 2013)

Thank you so much!  Yes, the scene is written, but the WIP is still being drafted, and it's great to hear from someone who's actually familiar with that model of Harley.  Super awesome!  He does magically manipulate the ignition as he drops down on the bike, but everything else is manual while his friend is jumping on the back behind him.

Here's the sequence as it's currently written...



> As he rounded the corner and came within sight of the coffee shop parking lot, Etienne spotted several guards emerging from the Moore Computer Securities gate and headed across the street to Kian.  The boy had slipped off the back of the bike and stood, helmet in hand, eyes turned up – he did not see them.  Throwing caution to the wind, Etienne broke into a run, leaning into the rig’s magic to push just a little more than human speed to get to Kian’s side.  The quick movement drew Kian’s eyes to him, and the boy smiled.
> 
> “Helmet!”
> 
> ...



Does this look realistic?

And thanks for the video!  It's very helpful.


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## Quillstine (Nov 12, 2013)

I'm hooked.... 
There is nothing in there that would make anyone think he is not on a Harley, or in a hurry!
My only suggestion, and this being so amazingly picky that I am blushing saying it! Me at all of 3 posts and never published or presented a single piece of work, giving you suggestion seems really...arrogant. So sorry if that's how it comes across.
I would say "onto the drivers seat" not "into the drivers seat". Into is technically correct, but makes me think of a car.


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## A. E. Lowan (Nov 12, 2013)

You're talking to the Evil Queen of Why - I like picky, hon.  Thanks for the heads up, I'll change it.


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## musycpyrate (Nov 16, 2013)

There is a lot of steps to get the bike started, in gear, and going. I do have an idea to keep the speed up though. It's called push starting. Last summer my battery went dead and to start it I turned the ignition to the on position, left the bike in first gear, then ran the bike down the street. I hopped on when I was going as fast as I could run, I let out the clutch and the bike started. Of course there is the chance it may not start but, at least the character could leave the bike in gear and in motion faster. Hope that helps. 

Starting A Motorcycle With A Dead Battery - YouTube


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## musycpyrate (Nov 16, 2013)

Since you have some magic involved you could try to magically push start the motorcycle. I have done this before, and it's really quite simple. You would still need to turn the ignition to on and put or leave the bike in first gear. Hold down the clutch and run with the bike a short ways, hop on, release the clutch, feather the gas and presto.... bike has started and rolling. Of course when I did it I took a couple of tries, but I think with magic you could make this scenario faster with this method. Hope this helps. 

Starting A Motorcycle With A Dead Battery - YouTube


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## musycpyrate (Nov 19, 2013)

Sorry for the double post.


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## Omnidragon22 (Nov 24, 2013)

if only our lives depended on it


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