When push comes to shove

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spook
Dolphin-headed purple plasma TLR thing?
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Joined: Mon Jan 29, 2007 7:12 pm
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When push comes to shove

Post by spook »

Can anyone tell me why modern road going sports bikes have push-pull cables? For instance my CBR929 (undergoing rebuild (lol)).. has such a set-up, though the butterfly rack also sports quite a heavy spring, that is responsible for the throttle valves return to idle seat. The return cable is never in tension. The only thing the push cable is doing that I can see is adding drag? Can anyone enlighten me? Cheers.

hotcam
Help!!! I need a LIFE!!!
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Post by hotcam »

Yes it does seem redundant. Off-road motocross racers have only a
single cable.

I heard that some old carbs could hold the throttle valve open in
the carb by suction if the return spring broke, thus the rule for
a pull-close cable.

It might be a requirement of safe design practise,
or it might be enshrined in legislation somewhere, but I couldn't find
it in ADRs.
-------
'95 FZR1040 '09 FZ1-S
"And they had a machine, a dream of a machine, with wheels and gears and perfect in every respect, and they lived on it..." -Stanislaw Lem, "Cyberiad"

spook
Dolphin-headed purple plasma TLR thing?
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Joined: Mon Jan 29, 2007 7:12 pm
Location: Melbourne. Australia

Post by spook »

Yep, I think your spot on Cam. I found this page in relation to RS flatslides. I don't envisage a problem with the 929. I'm going to run a 1/4 turn MX unit and see how it goes.

http://www.mikunioz.com/rs_accessories.htm

sickle44
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Post by sickle44 »

It is matter of safety, reliability, and precision, as more accuracy can be obtained with throttle position opposed to a single set-up which can at times get a little sloppy and loose, therefore, not as accurate positioning of the butterfly.
Michael
Yes Yes I know, I said, I'm building a project YZF1070

Basement is done now, 850 finished and gone...
Gotta get the new siding up on the house.
Fixing the FZ1 up, cleaning up garage and then I might even begin

hotcam
Help!!! I need a LIFE!!!
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Post by hotcam »

more accuracy can be obtained with throttle position opposed to a single set-up
True, but don't Yamaha normally recommend running the pull-close cable
adjusted with fair slack, so there is zero tension on it, to allow for
handlebars to turn etc?

If one did adjust one's cables so as they were precisely positive-acting
on the butterfly (same as the Exup cables), there would definitely
be precision.
But would the tension change slightly as handlebars were turned?
EXUP cables don't have to deal with any relative movement between the
master and slave pulleys.
Hmmm interesting aside but it probably doesn't make any difference.
-------
'95 FZR1040 '09 FZ1-S
"And they had a machine, a dream of a machine, with wheels and gears and perfect in every respect, and they lived on it..." -Stanislaw Lem, "Cyberiad"

spook
Dolphin-headed purple plasma TLR thing?
Posts: 3839
Joined: Mon Jan 29, 2007 7:12 pm
Location: Melbourne. Australia

Post by spook »

Single cable works fine, no worse than the dual. The bike only has 4000 klm on it, the butterfly's etc are in good condition, and the spring quite firm. They in fact bang shut. I don't think Stan is running the second cable on his fizzer either. It was Stan who suggested a thread on the subject... Interesting.

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