Back on a GRiSO at last

Well, back on a GRiSO at long last. I've not had one since a bad experience on my '06 1100 two or three years ago.
I was riding in the city traffic, 30 mph limit, just pulled away from a set of lights and snicked it into second gear then BANG, she took off like the proverbial scalded cat. Wide open throttle and two wheelies (yes!) in the space of less than 2 seconds and 50 yards. At no time did I dial in that amount of throttle, in fact I closed it and applied the brakes to no avail. I had no time to pull in the clutch, the front came down on a locked up front wheel (I had the brake on) washed out the front and I threw it down the road. No explanation ever found, NO it wasn't anything interfering with the throttle linkage, cables etc. Sold the bike with minimal damage and just 14k miles for £2000 last year, no way was I going to ride it without having some explanation for what happened. Some idiot on another forum said no big deal, probably not of it happens on a highway in a tall gear, but not in heavy traffic and second gear - try to wheelie a GRiSO, it's not easy!
Anyway, I've now bought a 2016 200SE because I just loved my GRiSO.
Incidentally I've just replaced the oil pressure switch on my V7 Classic, now the 1200 is suffering the same, common it seems, fault. And what a pain they are to reach!
Safe riding all from mrwrinkle in the UK.

Be gentle, Pete.

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Sounds scary mr wrinkle
Glad you survived and welcome!

Damn! I wish my Grisos do that... Wheelies on demand! Fuck yeah...

The problem with your hypothesis as to the bike's behaviour is that the only thing that changes the throttle plate angle is rider input. The W5AM throttlebody/EFI system is purely mechanical, it is not a 'Ride by wire' system where, theoretically, the throttle plates could open without a mechanical input if instructed to by the ECU, (Although this never happens as the RBW bikes have a three way failsafe system to make sure it doesn't.).

It is possible that something physically jammed open the throttle cam, although unlikely. The most plausible culprit being the gearbox breather hose if it was poorly positioned. Also if the cables were poorly routed the engine speed might rise if the bars are taken to full lock but not sufficiently to cause the bike to run away or wheely uncontrollably.

I fear it is most likely you simply lost control of the bike. As such I would suggest you approach riding your new bike with great caution as a similar mistake on a 1200 will achieve the same result, simply with more speed and force.

Hi Pete, thanks for your interest.
I am 65 years old and have been riding bikes for about 47 years. I spent some years as a motorcycle mechanic and have been involved in international bike racing as a team mechanic. My first reaction was to close (what little throttle) I had applied, remember I was in traffic in a 30 mph limit. With my firm grip on the twist grip how could the throttle (a) open wider than my input and (b) not shut when I closed it? Remember it did this twice in very close succession. I completely understand the logic behind the idea that I did something wrong or something interfered with the linkage. However, there is no firm explanation how, with a dual cable setup, the throttle bodies can work independently of the twist grip. I challenge anyone to replicate this and wheelie twice just using the throttle!!
I am just wondering if this thread should be continued somewhere else on the forum?

I have done a wheelie or two on my Sport - lowly old humble ditch pump, that it is. It is quite easy - once I just planted it in traffic in 1st gear, front wheel made me poo my pants a bit- the other time was getting off the lights and managed to drop the clutch with a fist full of revs, again front wheel goes up.

I have had the symptoms you describe though. Indeed it was something jammed in the throttle linkage on the R/H throttle body. I had blocked off the stepper motor with a long length of 8 mm (?) Allen head bolt, somehow it moved and jammed in the linkage - I didn't pop a wheelie but did manage to burn a pile of rubber from the rear tyre, under controlled ( I reckon I was barely in control) acceleration. I replaced this with a shorter bolt when I got home and the problem hasn't come back.

While our bikes are porky, long-legged and long wheel based, they are still capable of hooligan activities, whether intentional or accidental. A good rider (not me) can easily get the headlight pointing to the stars with little effort. Fortunately, very few of us ride this way, well not intentionally anyway. Torque it up and see what can be done... It's a quarter tonne handful if it all goes pear-shaped though.

mrwrinkle wrote:

Hi Pete, thanks for your interest.
I am 65 years old and have been riding bikes for about 47 years. I spent some years as a motorcycle mechanic and have been involved in international bike racing as a team mechanic. My first reaction was to close (what little throttle) I had applied, remember I was in traffic in a 30 mph limit. With my firm grip on the twist grip how could the throttle (a) open wider than my input and (b) not shut when I closed it? Remember it did this twice in very close succession. I completely understand the logic behind the idea that I did something wrong or something interfered with the linkage. However, there is no firm explanation how, with a dual cable setup, the throttle bodies can work independently of the twist grip. I challenge anyone to replicate this and wheelie twice just using the throttle!!
I am just wondering if this thread should be continued somewhere else on the forum?

Good. In which case you will understand that it is not possible for the machine to suddenly accelerate without human input. Sorry. You screwed up. Own it. There is no shame in that. We've all done it.

Commonly referred to as "Whiskey Throttle"

Been there a few times myself.

Motorcycle throttle design is basically wrong.
The feedback loop that turns (1) the bike moving off quickly into (2) you hanging on to the throttle grip and opening it wider, has probably been experienced by all of us at one time or another

lcjohnny wrote:

Motorcycle throttle design is basically wrong.
The feedback loop that turns (1) the bike moving off quickly into (2) you hanging on to the throttle grip and opening it wider, has probably been experienced by all of us at one time or another

This.

I'm convinced that had motorcycles only been invented in the last 30 years or so, they would never have been permitted to be operated on the roads.

Has any other system ever been tried? While I don't think it's the answer, I would have thought someone might have at least experimented with the ATV-style thumb throttle.

Very interesting. Unintended Acceleration on a motorcycle. There were cases on cars back a long time ago
where when a motor mount would break, the cable would snap back and off you went.
My first bike was a 73 Sportster which had a manual throttle return. Till this day I still try and return the
throttle manually. Maybe someday it might save my ass?

Happened to me on a borrowed 70’s kawi1000 , the initial surge caught me off even though I thought I knew what was coming , either way no damages other than my pride ....

I removed my throttle tube years ago. I've got one of the more well mannered GRiSOs out there and it always knows just the mood I'm in.

Elon Musk borrowed my GRiSO seven years ago to develop his driver assist mode on the Tesla.