Throttle

[jackspot]

Hi all ive just purchased a FZR600 that as been used solely as a track bike for the last few years ..My question is it looks like someone in the past as taken 1 of the throttle cables off .The guy i bought from says its not a prob having no return cable ..Im going to use it for a few trackdays do you recommend putting the return cable back on or would it be just fine as is
cheers
chris

[djalbin]

For a track bike, it depends on your riding style and the track. Some riders will remove the throttle return cable so the RPMs will not drop too quickly when they release the throttle. Other riders keep the throttle return cable but increase the idle RPMs. Both methods help provide partial throttle when releasing the throttle. It's a personal choice as to which method fits your riding style. No throttle return cable will allow the RPMs to drop slower when releasing the throttle. This slower decrease in RPMs can be useful for clutchless gear shifts and reducing the effects of engine braking. Riders who prefer more precise throttle control will keep the throttle return cable and just increase the idle RPMs. This keeps the RPMs from dropping too low when the throttle is fully released - reducing engine braking at the lower RPM range.
If you're always in the upper RPM range then no throttle return cable will help keep the RPMs elevated when releasing the throttle. If the RPMs will drop into the lower RPM range, and you want more precise control of the RPMs, then keeping the throttle return cable and increasing the idle settings will provide partial open throttle when the throttle is released (closed).
Added benefit of the increased idle settings is it keeps the coolant flowing better when you're at idle and not moving ... keeping the engine temperature lower.
And if it suits your riding style you can have both - no throttle return cable and increased idle RPM setting.

[jackspot]

Thanks for reply...interesting ive never removed a return cable so was more concerned that it wasnt going to do any lasting damage ..But like you say it must have been how the previous owner liked it on track
thanks

[willandrip]

For a track bike, it depends on your riding style and the track. Some riders will remove the throttle return cable so the RPMs will not drop too quickly when they release the throttle. Other riders keep the throttle return cable but increase the idle RPMs. Both methods help provide partial throttle when releasing the throttle. It's a personal choice as to which method fits your riding style. No throttle return cable will allow the RPMs to drop slower when releasing the throttle. This slower decrease in RPMs can be useful for clutchless gear shifts and reducing the effects of engine braking. Riders who prefer more precise throttle control will keep the throttle return cable and just increase the idle RPMs. This keeps the RPMs from dropping too low when the throttle is fully released - reducing engine braking at the lower RPM range.
If you're always in the upper RPM range then no throttle return cable will help keep the RPMs elevated when releasing the throttle. If the RPMs will drop into the lower RPM range, and you want more precise control of the RPMs, then keeping the throttle return cable and increasing the idle settings will provide partial open throttle when the throttle is released (closed).
Added benefit of the increased idle settings is it keeps the coolant flowing better when you're at idle and not moving ... keeping the engine temperature lower.
And if it suits your riding style you can have both - no throttle return cable and increased idle RPM setting.

Some parts of that cannot be correct surely ?;

The return cable would actually slow down the speed of carb closure; its job is to pull the twistgrip closed from the carb bank end not push the butterflies closed.

It is the springs in the carb bank that pull the butterflies closed not the return cable. The return cable is just an extra burden on the carb butterfly return springs by adding drag of the cable inner.
It is impossible to use the return cable to close the carb butterflies faster; the flexible braided cable would bunch and simply distort from its usual path . That would only work with a solid wire cable and be very unwieldly.

A single opening throttle cable has slightly less resistance at the twistgrip when opened and closed than that which has the return cable fitted.(lighter pull but hardly noticable).

N.B. If the closing cable is adjusted with insufficient play the throttle becomes very slow and hard to close which kind of proves the above points.

If a twistgrip is slow to close the carbs and you turn it manually closed to drop the engine rpm as fast as possible; it is not the closing cable pushing the cabs closed just that the twistgrip is badly fitted/lubricated and slowing down the carbs springs operation.

[djalbin]

But like you say it must have been how the previous owner liked it on track

You can always give it a try and see if you like it without a throttle return cable. Personally, I like it connected. If you do reconnect the throttle return cable than you can do as suggested by willandrip and play with the cable slack adjustment.

I do like the elevated idle RPM setting because the factory spec idle always seems too low to me.

Anyway, play with the settings (trial and error) and find what suits you best ... and enjoy the bike.

[Kevadlilleke]

Shouldn't the return cable actually be there to speed up butterfly closing if you actually bother to twist the throttle closed instead of removing your hand from the handlebar.

[willandrip]

^ How can it ?
A braided throttle cable that is not 100% fully sheathed through its entire length is incapable of pushing !
Even 100% sheathed it will still bunch inside the outer sheath and then once out of the end of the outer cover will simply distort.

Braided cables are only for pulling applications.

It would require a cable on the scale of the one used to operate the clutch to push anything.
It would be so unweildly one may well as use a hosepipe and fencing wire to fabricate a push cable.

It is extremely easy to test this;
Next time the airbox is removed, open the butterflies manually and hold them open with a finger.
Operate the twistgrip......the inner cables simply flop about.

The return throttle cable is utilised for the carb/s to pull the twistgrip closed not for the twistgrip to push the carbs closed.
The only way that moving a twistgrip closed manually speeds up closing the carb butterfly/slide is if the cable or twistgrip is dragging because of dirt/adjustment/lubrication/fitment issues.

A well set up throttle arrangement on a motorcycle should snap shut as fast as a tripped mousetrap and sound similar.

[Kevadlilleke]

Mechanically both cables operate on pulling. "Push" cable only refers to "pushing" the throttle grip. Exactly the same way the Exup servo operates on pull-pull.

Random illustrations from the web, I'm not near my bike:

[willandrip]

I am unsure if it is in the translation ,but your post make no sense !

[Kevadlilleke]

Good morning. I can't find a suitable illustration from the web, so I will draw one later Today.

[willandrip]

Keva....; It is this part

"Shouldn't the return cable actually be there to speed up butterfly closing if you actually bother to twist the throttle closed instead of removing your hand from the handlebar."

and then you stating both cables are "pull" cables that I am at a loss with !

There appears a lot of misinterpretation in the motorcycle fraternity regarding the so called "push" cable.
It is really the "return" cable and the carb/s springs return the twistgrip to the closed position by pulling on this cable.

Your post quoted above can only work if the return cable or twistgrip itself is dragging and the rider manually overcomes this by closing the twistgrip.
He/she is not using the cable to close the carbs ,only overcoming the drag that is preventing the carb springs from pulling
the twistgrip closed.

[DonTZ125]

Sorry, Will; I'm with Keva-smith. The 'closing / push' cable is there to positively close the butterflies, and is a safety / lawyer-liability feature added in case of damage to the open cable or the springs. For a track bike, carefully maintained and inspected, I'd just pitch it. For that matter, there are probably as many bikes running around with the close cable removed as with new, properly installed cables.

[jackspot]

Thanks for all your replys ..I must say the throttle operates very responsive .and as soon as i let it go it returns very snappy [ i like your term like a mouse trap ]..ive had the airbox off and it is very well maintained and well lubricated ..It certainly doesnt work any worse than the throttle on my FZ1 ..So thanks guys ill report back anyway because the first track day on it is in 2 weeks

[Asudef]

Could someone post a picture of their push cable at the throttle actuator?

I bought the Motion Pro cables and it doesn't fit my mount. After some searching on ebay, it looks like there's two types.



Those of you with this type of mount, how do your cable ends look/tighten down?