Sudden Unintended Acceleration

So…. There’s good news and there’s bad news. The good news is that I’m still alive. My friend Mark and I were planning on loading our swings on to a trailer and heading to Payson for a day long ride this weekend. We didn’t get far. I gave my bike a little gas to get it in the trailer and experienced what I have found is called “sudden unintended acceleration.”

The swing went up the ramp, crossed the trailer, hit the foot high guard on the rear of the trailer, launched through the air, cleared the trailer hitch, cleared the raised pickup gate, cleared the pickup bed and hit the rear window of the pickup truck. As the swing cleared the rear tailgate of the pickup, the nose pitched forward so I flew off from about ten feet in the air. I landed to the right side of the pickup, flat on my back on the cement side walk.


I took the swing to a local dealer. The service writer used to do accident investigation. They spent three hours tearing the bike apart and found the root cause. There was excessive free play in the throttle. The excess wire got caught on the guard that creates the channel for the throttle cable. When I rotated the throttle, it wrapped around the guard, moving around a much larger circumference. Essentially, I had an intermittent quick or drag throttle.

They found a 1/16 of an inch of movement would immediately open it to ½ to ¾ throttle. Also when doing slow maneuvers if the cable snapped off the guide, the throttle would slam shut with predictable consequences. Ironically, I had the parts on order to fix the problem, but crashed a few days before they arrived.

The swing is amazingly tough. It only had a bent handle bar and some scratched plastic. It will be fixed next week and I’ll be riding again. Fortunately for me I always wear my safety gear. If I didn’t, I would be dead. I ended up with a badly sprained ankle that makes it hard to walk and some bruises. All in all, it could have been much worse. Mark took pictures. What are friends for?

Sorry if this is a bit long. Please check your gear!

Hmmm.

Gosh!

What can one say?

Very glad to hear the Silverwing's okay - even gladder to hear you're relatively okay, too.
I hope the ankle heals soon - best wishes.

You're the first person I've ever heard use the Swing as a stunt bike!
I could not stop laughing as I was reading the description.

I know its no laughing matter to you, but in some states things like that are often preceeded by "Hold my beer and watch this."

Glad you and the bike are okay, but I have to be honest....
I'm disappointed there is no video.

At least the bike was already loaded to take to the dealer.

After the fact it was pretty funny! If we had video it would have made TV. I'm glad we got the pictures. The really scary part is that we were both sober (actually neither of us drink) and the bike did this from a complete stop only three feet from the ramp. I had no idea a swing could do that. You should have seen the look on the dealers face when I described the incident, then told him it was a swing!

That's some mean parking! but I'm curious why not ride the SW's to Payson?

Only because it was still pretty hot out. Not so much when leaving, but coming back would be a bit warm. I think that weekend it was going to be 110.

Day to day owner maint. You should have noticed excessive play in throttle cable and fixed.

Could have been worse in traffic.

Skrone wrote:

I had no idea a swing could do that.

50 odd HP with a 1/4 inch rotation via a twist throttle!!!! Come on?

Have you never had someone twist the throttle of any auto bike when stationary? The results are quite amazing, (as you now know.) Someone did it to me on a 50 cc machine and the scoot flew from under my seat taking the clown who thought it was funny with it.

So 585 cc having it's throttle blipped was always going to be lively!!!!!!!

Moral

Always walk your beast onto a trailer.

John Grinsel,

Read what the OP wrote:

"Ironically, I had the parts on order to fix the problem, but crashed a few days before they arrived. The service writer used to do accident investigation. They spent three hours tearing the bike apart and found the root cause. There was excessive free play in the throttle. "
Your average recreational biker wouldn't diagnose that relationship in a year.

The OP knew the problem existed but had no idea the relationship existed between the problem and the results it caused, even though like you he does some of his own maintenance.

Please try to be more tolerant and less judgemental.

And remember that not all of us are gearheads, nor do we want to be.
We expect to twist and go reliably and pay others to do the maintenance.
Because we are not experienced on that side of things, we don't always notice minute details and even when we do, at $75-90/hr for a mechanic we only take it in when we know something is wrong that we think is dangerous.

Could we avoid more headaches by learning more? Sure.
But putting someone down because they didn't isn't going to solve anything or endear you to anyone....quite the opposite.
Not everybody is mechanically inclined. Me...I'm mechanically reclined.
That's what I do while somebody else does the repairs.

Hard to be less critical-----bike also has brakes and kill switch.

Putting up on ramp, left brake handle can be used as kinda of a clutch as power is fed in....to keep things under control.

No comment on trailer biking.

john grinsel wrote:

bike also has brakes and kill switch.

This is true. These are definitely logical alternatives.
I'm sure you'll agree its a bit of a challenge to think logically in the middle of panicing and holding on for dear life.
If you are trained to think and act quickly in tough situations like a soldier is, or a rider with a million miles of experience, perhaps you think of these things.
I first have to come to the realization I'm panicing, then choose not to panic, then assess my options, then make a decision.

If I were in the OP's situation, my thoughts would be,
1. Panic
2. Why am I on the ground?
I don't think I would have time for anything in between.

But John, thank you for trying to be less critical.

How come you dont delete "his" posts?

Tagg wrote:

How come you dont delete "his" posts?

Attacking or maligning other members will not be tolerated.

maligning
noun
the making of false statements that damage another's reputation.

Tagg wrote:

maligning
noun
the making of false statements that damage another's reputation.

http://www.merriam-webster.com/dictionary/malign

1 a : evil in nature, influence, or effect : injurious b : malignant, virulent

2 : having or showing intense often vicious ill will : malevolent

What'd I do?

I have loaded alot of vehicles onto trailers. even without any mechanical issues, I have accidently slammed golf cart, lawnmowers, toys in general into the front of the trailer. The combination of the slack in the reese hitch and ball makes the trailor lurch back, then as you approach the top of the ramp the trailor reverses and slams back forward shot - putting you forward. all that sometimes makes you lean on the gas for just a second. too late. especially before 6:00 AM. I did put a golf cart over the front one foot high wall by accident loading it. things can happen real quick. Now I load very slowly.

Hey John,

Yes the bike has brakes and a kill switch. The kill switch by the way won't actually stop the bike. It will only stop accelerating the bike. If you understood the mechanics of the situation you would realize given the greater than usual acceleration and the short distance to stop there would be no way to safely stop before being flung off the back of the trailer. Once I crossed 1/2 the trailer at that speed, I was pretty much going over the trailer no matter what.

The point of my post wasn't to debate what your imagined super human reflexes could do in the same situation. It was to point out the highly unexpected consequences of excessive free play in the throttle. The bike had a safety inspection from a Honda dealer two weeks prior to the accident. That's where I found out about the free play and promptly ordered the parts.

I don't know if Honda will be entering this data in their system or warning current owners of the problem. That is why I am posting here.

Oh Skrone, you're in for a light sabre whupping! :lol!: Seriously, if you have one person check for throttle free play and prevent an accident, they will thank you.

Quote from movie "Thunderheart":

Hey , You sound like a bunch of Old Women! Quit it and come on up and watch TV.


MaxB (hehehehehe)

MaxB wrote:

Quote from movie "Thunderheart":

Hey , You sound like a bunch of Old Women! Quit it and come on up and watch TV.


MaxB (hehehehehe)

That one went over my head!!!!!

No idea what your on about!

Hey Hi Yo

That's what I was shooting for. Even the Honda service writer that found the throttle free play wasn't aware of the possible consequences. I just wanted everyone to know so they could check their swings and get 'em fixed.

I get the bike back today! and from now on I will definitely be walking the bike on to the trailer!

explain some more on this "excessive throttle free play " and what parts are needed to correct it ? cause i don't like the idea of my s-wing becoming a stunt bike on a whim ...

Rednecks favorite last line "watch this"

Hey Moonshiner,

When you turn your throttle, it should rotate a small amount before it starts pulling the throttle cable. The key here is small amount. If it turns too far before meeting resistance that means there's too much cable floating around inside the throttle handle that can get caught on things.

Stu