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Old 01-07-2014, 05:01 PM   #1
mopulga OP
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Bing throttle cable travel length

Yo everybody,
Help please. Anyone know the length of cable travel on the traditional Bing Carb?

OEM cable "Free length" is described as 72mm, but I am actually seeking to find cable travel length for a new set of aftermarket throttles which supposed to have 57mm of travel. The other rate limiting function is a splitter that will be used with probably has some limitations as well.

I know... this is complicated. I am modernizing the controls and simplifying them at the same time.
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Old 01-07-2014, 05:19 PM   #2
patrkbukly
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Quote:
Originally Posted by mopulga View Post
Yo everybody,
Help please. Anyone know the length of cable travel on the traditional Bing Carb?

OEM cable "Free length" is described as 72mm, but I am actually seeking to find cable travel length for a new set of aftermarket throttles which supposed to have 57mm of travel. The other rate limiting function is a splitter that will be used with probably has some limitations as well.

I know... this is complicated. I am modernizing the controls and simplifying them at the same time.
I bought some aftermarket throttle cables on ebay for my PD. After installing them from start to finish thinking I had done something wrong, come to figure out they were about 5MM shorter…setting idle at the lowest point at about 3200 RPM's.

I finally pulled them off the 3rd time thinking WTF am I doing wrong, laid them side by side to the originals and realized te length difference. I returned them, and bought new at my local dealer almost as cheap and never looked back.

Just saying.
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Old 01-08-2014, 11:10 AM   #3
mark1305
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To elaborate on what he said.... It's not only the travel dimension that matters, but rather the free length. It must be appropriate for the required travel at the carb lever plus the distance to the point at which the ferrule on the sheath bottoms into the socket on the carb. Factoring in a splitter adds to the challenge to get it right.

Not saying it can't be done, but there are multiple factors to match up.
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Old 01-08-2014, 09:47 PM   #4
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theres a chart at Antons that might help:

http://largiader.com/articles/cables/
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Old 01-09-2014, 12:09 AM   #5
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I agree with Mark1305:
Quote:
Originally Posted by mark1305 View Post
there are multiple factors to match up.
The free length required in a cable takes into account how much is taken up by:
1. The distance between the outer and the end of inner within the throttle control when fully backed off.

2. The distance between the outer and inner at the carb, with the idle screw backed off (not touching the throttle arm) and the cable adjuster fully screwed down (maximum slack in the cable)

3. The amount of adjustment available in the cable adjuster at the carb, to take up any slack.

I think these are all measurements you will have to make yourself for your own setup.

1 and 2 are clearly fixed distances with 3 having a range of measurement.

The cable free length required will be 1 +2 + half of 3, which should ensure that with the slack just taken up, the adjuster is in the middle of its range of adjustment. Having done the calculation, you need to see if a stock cable is suitable or if a custom cable is required.

Once you have the correct cable, taking account of the above and properly adjusted, the final piece of the puzzle is to ensure that the new throttle control can provide enough movement (pull) on the cable inner to move the throttle arm on the carb through its full distance, from fully closed to fully open.

Realistically, if the throttle control can't do this you should consider going back to the stock one. Alternatively you will need to engineer a device to multiply the movement appropriately, such as some kind of lever mechanism, which starts to get complex...

Splitters are usually a 1:1 ratio, so unless there is wear in it or it operates at a different multiplier, this should not be relevant.

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Old 01-10-2014, 06:41 AM   #6
Beemerboff
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Ordered a new throttle cable for my BSA recently, and it came with four different loose nipples , about a foot extra inner length, six inches extra outer length, a mid cable length adjuster and six loose ferrules.

They must have given up on trying to work out the endless permutations of what could be fitted to these older bikes and just covered all bases.

Which was perfect for me, anyway.

I had a set of these 5mm short cables too- still in sealed bags, with the correct bike and carb size on the label, but hat close to correct that I spent hours trying to work out what I was doing wrong.
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Old 01-10-2014, 06:49 AM   #7
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Quote:
Originally Posted by mopulga View Post
I am actually seeking to find cable travel length for a new set of aftermarket throttles which supposed to have 57mm of travel. The other rate limiting function is a splitter that will be used with probably has some limitations as well.
The splitter limits travel.
travel length can be increased by modifying (shaving) the shuttle.
Magura make a replacement that gives 60 mm of travel.
Next limitation is the cam on the crown wheel in the twist grip assembly.
50mm is about the max std.
A self tapping screw in the side of the crown wheel increases the cam profile and gives a bit extra pull length.
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Old 01-10-2014, 12:50 PM   #8
Padmei
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Does your after market throttle have 2 cables? I bought a set of universal adjustable cables that have adjustment in the middle of about 30-40mm. I didn't want a splitter.
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Old 01-10-2014, 01:08 PM   #9
mopulga OP
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good discussion. I was wanting to know the travel length before I bought the throttle.

That being said, was not able to estimate travel length with the different matters that make this complicated. I did reach out to BellissiMoto who has a domino throttle which I have been wanting and they allowed me to try and test the throttle which is coming this weekend and return if the advance was not not enough.

Will maybe know this weekend.
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Old 11-24-2014, 11:51 PM   #10
bleaknessengine
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not too old a thread, I guess...

what style of throttle/one into two throttle cable would be able to open the bings on an R90/6? The venhill splitter says it only allows for 40mm of cable travel, but unless my head is mindfudged about the chart on anton's site, I need more than that? What with the free length and all...

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Old 11-30-2014, 12:50 AM   #11
Beemerboff
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If you have 32 mm carbs it appears from Antons site you want about 62 mmn of inner cable below the bottom of the adjuster on the carb, to reach down to the lever which turns the butterfly.

So wind the throttle full open, and measure how much inner cable is still showing. On my G/S it is around 32/35 mm , indicating it takes approx 30 mm cable movement to open the butterfly. So 40 mm splitter movement should do. But I have a pulled muscle in my back so didnt spent a lot of time measuring, so check my measurements.

Note too that the Venhil splitter kit doesnt have adjusters at the splitter, so you will need an additional inline adjuster between the splitter and the twistgrip, which is not in the kit.

Just made up three sets of cables from Venhill kits, so things are fresh in my mind -------.
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