Throttle Spring

[Dickf]

I am a waiter...'06AE, I guess due in May. So, I have been hanging around the forum a bit to see what I can pick up. One of the things I learned was that FJR owners are even more frustrated that I have been about throttle return springs. In my youth, Harleys had no throttle return springs (as God intended), although Brit bikes did. Then along can Joan Claybrook, the safety Nazis, and the rest is history. I must admit, though, with multiple carbs or throttle bodies, torsion return springs are probably necessary to keep everything synched.

Anyhoo, in recent years (30 years or so) I have always used throttle locks of one sort or another but always found them something of a pain, compared with no return spring. Finally I devised a method for counter-acting the return springs. On my current Honda CBR100F, I add a torsion spring to the end of the twist grip in the place normally occupied by the bar end weight.

The idea is to have a twist grip torsion spring trying to open the throttle while the carb torsion springs are trying to close the throttle(s). Of course, the spring tension will never be a perfect counter-ballance because one spring is relaxing while the other (set) is tightening. If a light enough spring is chosen so that a maximum number of turns can be used, the the twist grip spring is reasonably linear in torque. You set the twist grip spring so it almost starts to open the throttle at idle. As you open the throttle more, the carb springs become relatively stronger. There is enough system friction in my Honda so that at crusie speeds I can remove my hand completely from the grip and the throttle will not move. At full open throttle, it backs down a bit, which is OK with me.

When I get my AE, I plan to fit a similar device. In the meantime some of you owners my like to experiment with your own installation. Photos below may help. Of course, details will differ between the Honda device and any FJR implementation

**** Frederick

 

[radman]

? Disconnect the center spring and the remaining two provide a gentle return action and are pleasant on the wrist. A proven FJR solution.

 

[Fallen Jim Rides again]

I realize it is unlikely, but what happens if the return spring surrenders? Wouldn't the throttle whack itself wide open? Hmmm. I think I'd stick with Rads advice on this one.

 

[radman]

I realize it is unlikely, but what happens if the return spring surrenders? Wouldn't the throttle whack itself wide open? Hmmm. I think I'd stick with Rads advice on this one.

Nothing. Remember that the Feej is a push-pull system, you really don't need any return spring at all-just twist back to close the throttle.

 

[Fallen Jim Rides again]

I realize it is unlikely, but what happens if the return spring surrenders? Wouldn't the throttle whack itself wide open? Hmmm. I think I'd stick with Rads advice on this one.

Nothing. Remember that the Feej is a push-pull system, you really don't need any return spring at all-just twist back to close the throttle.

Oops, sorry. I was refering to the modified throttle shown above. Doesn't it use a spring that is pulling the throttle open against the return spring? If so, wouldn't it pull the throttle open if the return spring were to (again unlikely) fail?

Or did I just miss something important? :blink:

Edit: I do realize that you could push the throttle closed. but having to do so is counter intuitive, or would be for me at least. Bigger issue is that the whole point is the ability to operate the system with the hand off the throttle.

Murphy scares me.

 

[Dickf]

Well, I will admit that if you don't know which way to rotate the throttle grip when you want "off", you have a problem. As a matter of fact I remember this as being an important briefing item when I let friends ride my '58 Harley FLH. Don't forget that there arre probably more than one return spring on the bank of carbs (or the throttle body). Then again, on the FJR, I dunno. I do know that a lot of energy has been expended on methods of keeping the throttle set, and I do not want to have to mess with a throttle lock (or cruise control) if I don't have to. Also, now all I have to do is lay my hand on the right grip, covering the brake lever and ajust speed with my palm. Sort oflike the old days.

****

 

[RadioHowie]

Wouldn't you get the same effect simply by disconnecting the return springs at the throttle bodies?

Then you haven't butchered up your handgrips and rube-goldberg'd your throttle assy.

Not to mention the possibility of liability if you run into someone and your "modified" throttle is noticed? Litigious times we live in, y'know.

 

[Dickf]

At least on by CBR1000F, with carbs, something has to keep all four pots returning to idle. The throttle cable merely rotates a rod which pushes all butterflies open. Individual torsion springs keep them tight against the stop. Can't mess with that, and wouldn't want to. Also, the "return" cable on this bike does absolutely nothing - it is the set of return torsion springs on the throttle shaft that does the returning. I suppose the return cable is therre for liability reasons.

Speaking of liability, I certainly would not try to sell anthing like this, but I don't see how it is different than a throttle lock (sold every day) - except that my spring arrangement is easier to roll to idle. From a moral standpoint, who do you think is going to do more damage, an old boy who dies on his bike with the throttle locked, or the same old boy who has the big one dirving his Surban/Expedition/etc. with cruise control set?

****

 

[Constant Mesh]

The '06s are expected to have a redesigned throttle pulley that should be easier on the wrist. Yamaha refers to it as a "counter-progressive throttle pulley".

This new pulley may offer a less sensitive throttle for less than 1/2 throttle operation.