Topic: Purpose of the throttle return cable?

[Quattrocilindri]

I really don't see what function the return cable has. If the inner cable was a stiff, rigid, single wire, I could see the push back to return as a safety feature. Of course, such a design would make for a very stiff throttle. But a flexible return cable cable seems very redundant to me.

Any one has removed it and has  good things to say about the mod?
Seems to me that my 350F throttle should take less effort; I have checked the routing, lubed the the cables after disconnecting them at both ends; they slide friction-free. But perhaps the original carb return springs may be a bit too stiff, or I may just be getting old.

Any comments welcome..... 

[carnivorous chicken]

It is a safety feature, but it's redundant. I've ridden my 350F with a single cable for 25+ years without an issue.

Sounds like you've checked the likely suspects. Could be the spring, but you also might try lubing the inside of the throttle tube housing with just a little grease to help ease movement, and some on the handlebar. Could help.

[jonda500]

+1  lube the handle bar under the twist grip

the return cable doesn't push, it pulls the cable butterfly back!
John

[BenelliSEI]

It’s there “just in case”. I leave it a bit slack, but always hook it up.

[bryanj]

It has been noted, but not often, that the return spring can break and then the throttle would stick at wot.

Try convincing your insurance company that a factory fitted safety part isnt necessary

[PeWe]

Cable can make the throttle to go  harder and return slow.
 I should never ride my bikes without a return cable.
My life depends on a quick throttle off, everytime.

[Quattrocilindri]

My 350F and 400F have been the only bikes I have had with this feature, and I see that the Japanese had a sound engineering design, that, along with the ignition kill switch next to it, have completely eliminated the stuck wide-open throttle event from killing riders.
But I have owned several European bikes and Vespa scooters over the last 50 years that never had this second cable in addition to the kill switch. Never once I have had a stuck open throttle; my only concern is with the extra effort required with the throttle. Someone on this forum has suggested to stretch the return spring a 1/4" to make it easier on the wrist. how many of you have done this?

[Bodi]

The SOHC4  Keihin 4 cylinder carb rack has a single return spring. Bikes with direct cable operated carbs have a return spring on every slide: the early CB750s had a 1 to 4 throttle cable splitter and cable actuated slides, each with its own return spring. And no "off" throttle cable. A stuck slide would only affect one cylinder.
Maybe it's an abundance of caution, but a 750 stuck at WOT would be pretty damned exciting... and in a panic bad decisions are made. You can pull the clutch and grenade the engine or hit the kill switch, and either way be coasting in what could be a very dangerous traffic situation. The return cable lets you put a lot of force towards closing a stuck slide.
All the old twins - 4 and 2 stroke - that I'm familiar with had a cable splitter and cable carbs. Singles all had cable carbs.
I'm not sure what Kawasaki and Yamaha did with their carbureted fours. Probably used similar racks with dual cable throttles.

I would not ride a dual cable bike without the return cable. It should be adjusted to be under no tension (unless needed) and thus not cause much added throttle effort.
Stiff throttle is either from an overly strong return spring (not horribly difficult to remedy) or misrouted and/or unlubricated cables - or the adjustments have the cables tight against each other, there should be a few degrees of throttle play between open and close.

[BenelliSEI]

The SOHC4  Keihin 4 cylinder carb rack has a single return spring. Bikes with direct cable operated carbs have a return spring on every slide: the early CB750s had a 1 to 4 throttle cable splitter and cable actuated slides, each with its own return spring. And no "off" throttle cable. A stuck slide would only affect one cylinder.
Maybe it's an abundance of caution, but a 750 stuck at WOT would be pretty damned exciting... and in a panic bad decisions are made. You can pull the clutch and grenade the engine or hit the kill switch, and either way be coasting in what could be a very dangerous traffic situation. The return cable lets you put a lot of force towards closing a stuck slide.
All the old twins - 4 and 2 stroke - that I'm familiar with had a cable splitter and cable carbs. Singles all had cable carbs.
I'm not sure what Kawasaki and Yamaha did with their carbureted fours. Probably used similar racks with dual cable throttles.

I would not ride a dual cable bike without the return cable. It should be adjusted to be under no tension (unless needed) and thus not cause much added throttle effort.
Stiff throttle is either from an overly strong return spring (not horribly difficult to remedy) or misrouted and/or unlubricated cables - or the adjustments have the cables tight against each other, there should be a few degrees of throttle play between open and close.

...... what he said. +1.

[Quattrocilindri]

Thank you all for all your insight. I was not aware that Kehin carb slides have no springs, unlike my past bikes.
At this point, I am looking at increasing my hand leverage with the thick grips in the ad below:

https://www.ebay.com/itm/310433764149?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3Ddf1360169e534207ab937624097ad225%26pid%3D100675%26rk%3D1%26rkt%3D15%26mehot%3Dpp%26sd%3D310433764149%26itm%3D310433764149%26pmt%3D1%26noa%3D1%26pg%3D2380057%26brand%3D2FastMoto&_trksid=p2380057.c100675.m4236&_trkparms=pageci%3A0680b1ea-a8e0-11eb-afe8-52c8affb1681%7Cparentrq%3A1d704e7e1790a7b0e2012bd9ffd5c58f%7Ciid%3A1

I have had these on most of my previous bikes; or find a longer/weaker spring to replace the stock one.