Double throttle cables. Why do we need 'em?

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8/15/2021 4:55 PM
Edited Date/Time: 8/15/2021 5:07 PM

Ok- I've wondered about this for a long time, and I've heard various answers, most of which I'm not sure are still valid. I have faith in the OEM's so I'm sure they're necessary, just don't believe I've heard why.

Four strokes have 'em. Have forever. I believe the original reason was something to do with avoiding having the carb hang up open due to some sort of vacuum/pressure thing that could happen with the 4. With current electronic fuel injection, that reason would be antiquated.

So if it's something to do with the actuation of the throttle body, (that's why the FE 2-strokes have them), then why were they really needed with the older non-FE 4 strokes. Seems like a conspiracy to sell more cables.

I ran a '79 KLX 250 in some vintage XC racing, and changed the throttle control out to a single cable. No issues. I get that old, underpowered lump might be an apple to today's oranges, so educate me.

Tell me why we need the extra weight and complexity. Fer reals.

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8/15/2021 4:58 PM

Because they aren’t quads.

Quads have a single cable, but double the wheels. Bikes have double cable and half the wheels.

Q.E.D

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8/15/2021 5:00 PM

The return cable means you don’t need as strong a spring so the pull is easier and smoother since the return cable isn’t wrapped to the bottom of the tube.

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8/15/2021 5:04 PM

What would the weight gain or reward be for fly by wire throttle?

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8/15/2021 5:12 PM

Wonder how long until it’s electronic.

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GP740
Since 1987

8/15/2021 5:16 PM

GeorgiePorgie wrote:

Wonder how long until it’s electronic.

That will be pretty great, no more adjusting the idle, you set a rpm and it just goes there every time. I ride from 500ft to 13,000ft and even with EFI I have to fuck with the idle every couple thousand feet.

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I work to provide for my family, I ride to keep my sanity.

8/15/2021 5:47 PM

Because, science!

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8/15/2021 6:34 PM

I wondered the same thing 23 years ago when I got my 1998 YZ 400F. And still dont have an answer for you.

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The poster formerly known as Sir Roostsalot.

8/15/2021 7:33 PM

I think it's a safety carryover from early 4 stokes that could cause the slide to stick slightly from vacuum and the push cable would force the slide shut.

Obviously not an issue in FI now but one cold argue that they are still a safety feature to have two cables in the event the pull cable is frayed, pinched broken, the push cable can still close the throttle.

/shrugs.

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8/15/2021 7:44 PM

On KTM's the 2nd cable also turns off the choke/enrichener mechanism. Without it you'd have to stick your hand in there and burn it on the pipe.

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Powerband in every gear !

8/15/2021 8:02 PM

lawyers

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8/15/2021 8:14 PM

Wonder if APs bike has a single or dual cable

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8/15/2021 9:15 PM

endurox wrote:

lawyers

Yup. As others have said it is to prevent the slim chance of the vacuum sticking the throttle open.
So it is a liability CYA thing.

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8/15/2021 11:49 PM

No good reason that trumps the extra expense, friction and bulk.

Millions of smaller four strokes and plenty of larger ones- all older Pommy, Euro bikes did fine with one.

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8/15/2021 11:50 PM

Derpin' DJ wrote:

Wonder if APs bike has a single or dual cable

Appears to have 2 from the grainy footage while it was being wheeled away.

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8/16/2021 12:42 AM

You can pull the return cable out, it will feel like 2 stoke throttle, Light
You leave the housing to keep dirt out of both ends
Some Euros runs this

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8/16/2021 1:53 AM

Factor E wrote:

You can pull the return cable out, it will feel like 2 stoke throttle, Light
You leave the housing to keep dirt out of both ...more

Why wouldn’t they just run a plug?

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8/16/2021 1:58 AM

Butterfly vs slide but I'm sure most riders have seen more slides get stuck on 2stroke carbs than FI butterflies getting stuck, if ever.

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8/16/2021 11:03 AM

This is a great pic from another thread

AP pic shows 2 cables..

https://p.vitalmx.com/photos/forums/2021/08/15/505858/s1600_IMG_4965.jpg

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