Throttle cable adjustment musings

[George R. Young]

The throttle return to closed on my 2001 Concours lacked 'snap' so I decided to oil and adjust the cables. Mother Nature cooperated and it was warm enough in the unheated Ottawa garage (Feb. 16, 2016) to work on the bike, although it was snowy outside (50 cm).

Disassembled the throttle/switch housing and drizzled some 3-in-1 oil down each cable until things moved freely. Loosened up the return cable down at the carbs to make sure the return cable was not preventing the throttle from snapping closed.

Made my first discovery when trying to reassemble the throttle/switch housing, a task which seems to need 3 hands while I have only 2.

Other motorcycle throttles have a mechanical stop that limits rolling the throttle tube forward. Throttle play is the slop between this mechanical stop and when there is tension in the pull cable. And there's usually an adjustor to set the pull cable play. The play in the return cable is adjusted separately, with its own adjustor at the bar. On the SV650S, I increased return cable tension until the throttle closing was slightly slowed.

The Concours throttle is different - there's no mechanical stop. When you close the Concours throttle, you go past the point where the carbs close until you use up all the play in the return cable. This sort of explains why there's only one adjustor at the handlebar.

There is an unfortunate side effect. If you want to have minimal throttle play for nice, crisp throttle response, there will be lots of tension in the two cables, and the throttle closing will not 'snap'. If you adjust for more play, the throttle will 'snap' closed nicely when released, but you'll have to crank the throttle tube quite a bit before the carbs start to open.

I've compromised on "closes fully if not rapidly when released".

[MAN OF BLUES]

years ago I stumbled upon the way the conni throttle's function has a major flaw....
while its always a good idea to have a spare throttle cable, I never experienced a "pull" cable failure, but nave had 2 return cables snap... and both on the road hundreds of miles from home... when this occurrs, you end up having to add an additional cobbled in spring for return, to make it home, you can find them at most hardware stores, and install in the lot if you carry good tools....

now to the reasoning for failur;
I try to be gentle on the right grip when rolling the bike around the garage, or other places. during that process, I simply press against the right grip, and do not let it twist, but it seems as this has the culpret, as there is no positive stop in the housing, you end up putting a lot of tension on the return cable, and after time, it snaps... when it does, the throttle will still work, but when you manually shut it off, it rotates wayyyy past home, and becomes dangerous, it can actully cause the pull cable to disloddge down at the carb bodies... not good.

Now I have a return cable in my tool kit at all times, or even a better solution is to run the spare right alongside the existing one, taped to it every 6" along its length, so you simply switch the ends if one fails.

ymmv, be safe.

[George R. Young]

With my newfound understanding of how the Concours throttle is designed (no mechanical stop), here's how I think throttle cable play should be adjusted.

First, add a lot of slop to the pull cable with the adjustor at the throttle.

When closing, the throttle tube moves past the point where the carbs close, to the point where further motion is stopped by tension in the return cable.

The second step is to adjust the return cable until you're happy with the position where the throttle comes to rest. For example, if you need more adjustment in the pull cable, you can lengthen the return cable housing. The adjustor is conveniently located down at the carb end, and you only have to take half the fairing and the tank off to get to it. I was happy with the way it came. Hopefully at this stage, the cables are lubed and when you fully open the throttle and release, it snaps back to closed.

At this point, there's still lots of slop in the pull cable. So third, add tension to the pull cable until there is about 2 - 3 mm between carb closing (click) and banging into the return cable stop. This may impact the self-closing capability of the throttle. I had to loosen my pull cable a bit from this optimum until it would close all the way from fully open by itself.

I did all this and the throttle closes when released but it still has more total slop than I would like.

This design is right up there on the list of things I don't like about the Concours:
-throttle design
-pitted cams
-positive neutral finder
-light duty front wheel bearings