looking for Amal cable routing help

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Jul 8, 2007
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I searched the forum archives but didn't find any posts on this topic. The bike is a 73 850 Roadster. Carb internals are in good order. Just finished setting up the Boyer timing with a strobe. Bike starts easily and idles on both cylinders.

Before trying to set the idle speed and sync the carbs, I want to get the throttle and choke cables setup with proper routing and slack. I replaced the throttle cables from the 2-1 junctions to the slides as the outer cable housings were kinked and failing.

Ideally I could use a picture of where the junctions should be, relative to the carbs and to each other. I didn't find such an image in the factory, Clymer, Haynes manuals. I suspect that the throttle and choke cables interfere with each other a little at the carb, each forcing the other out of alignment, which can't help smooth cable operation. I also suspect the junctions are too far forward, forcing the cables to bend forward immediately when they emerge from the carb top.

Is it correct that both cables for each carb should come straight up from the carb and make a nice smooth 90 bend before heading for their junctions?

Should the junctions be tied to the frame? If so, side by side, one on top of the other, and where?

Thank you for reading this post!

Best regards,
Ken
San Jose, California

69 Rocket 3
73 Roadster
74 Duc GT
 

L.A.B.

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kenward1000 said:
Ideally I could use a picture of where the junctions should be, relative to the carbs and to each other. I didn't find such an image in the factory, Clymer, Haynes manuals. I suspect that the throttle and choke cables interfere with each other a little at the carb, each forcing the other out of alignment, which can't help smooth cable operation. I also suspect the junctions are too far forward, forcing the cables to bend forward immediately when they emerge from the carb top.

Is it correct that both cables for each carb should come straight up from the carb and make a nice smooth 90 bend before heading for their junctions?

Should the junctions be tied to the frame? If so, side by side, one on top of the other, and where?

I would really suggest that you route the cables to suit your own bike, as cable lengths, choke lever positions and handlebar types can be different? And while a certain cable routing may suit one particular bike it may well not suit another because of the things I've mentioned.

However, the following cable routing description works for me on my 850 Mk3 Roadster with normal Roadster bars:

THROTTLE
The left-hand carb throttle cable exits the carb top and curves forward, along and then crosses under the spine tube through the space between the spine tube and the smaller tube to meet the throttle junction which is positioned below and to the right of the spine tube, and the right-hand throttle cable exits the carb and curves forward alongside the spine tube and more or less, goes straight to the throttle junction.
The single upper throttle cable exits the junction passes between the frame and fuel tank and then curves up and around the front of the right fork headlamp bracket and then goes to the twist grip.

Sorry about the photo quality, - but I think you will be able to see roughly where everything goes?






CHOKE
The lower choke cable routing being roughly a mirror image of the throttle cable layout, as the left-hand choke cable goes forward along the spine tube to the choke junction that is on the left side, and the right cable goes forward and then crosses under the spine tube to the choke junction. The upper choke cable then passes around the front of the headstock from left to right and up through the gap between the console and the top yoke (only 850 Mk3 has the console) the cable then goes to the choke lever, which on my own Mk3 Commando is on the right-hand side of the handlebar. Many Commandos had a choke lever on the left side of the handlebar in which case it could be better to have both of the junctions on the right-hand side?




I do tie all cables and wiring to the frame, but not too tightly.
 
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Ken, the problems that you're talking about are pretty well part of the package and are the main reason that I now run a Tommaselli twin-pull twist grip with cables running individually down each side.

The exact amount of room that you have will depend upon the individual tank fitted but the cables will always have an easier life if you make a set up with 45° bends where they exit the carbs (robbing these fittings from old j*p cables is the easiest way.

Many of us find the chokes superfluous on the Commando and deleting them and plugging the entry holes also gains some space. I have a theory (unproven) that the chokes can make for a poor throttle action by binding on the internal faces of the slides, even when they are pulled out of the way. My throttle seemed smoother and lighter when I had deleted the choke slides but I am a master of self-delusion when it comes to modifying motorcycles :)

I agree with L.A.B. that loosely fixing the cables is a good idea, to make sure that they stay in the correct place when refitting tank etc. They shouldn't clamp the outer
 
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I am a master of self-delusion when it comes to modifying motorcycles
I can really relate to that!

I love that line. Can I use it?
 
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JimC said:
I love that line. Can I use it?
By all means Jim - If you understand it then you're qualified to use it :)

(of course, it helps if you've got things like piles of wheels in every imaginable size and an unimaginable range of Amal jets and slides and then have to confess that you're currently back to standard :)

Thanks for helping me realise that I've just summed up the last thirty years of my existence ! I've added it to my profile now !
 
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(of course, it helps if you've got things like piles of wheels in every imaginable size and an unimaginable range of Amal jets and slides and then have to confess that you're currently back to standard
I damn near split a gut reading that one. So true, so true!
 
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re: Amal cable routing

Thank you very much for the images and information! This was exactly what I was looking for. I agree completely about adjusting things to suit the bike configuration itself; I was merely looking for a good starting point.

I ended up with the throttle junction tied to the right side of the frame tube which under the spine, and the choke junction tied on the opposite side though a little farther aft as the choke cable is a little farther aft on each Amal; the choke lever is on the left handlebar. The cables come out of the carb tops nearly vertically before making a graceful arc to the junctions, with nothing to cause deviation from a direct path. I did tie the cables in several spots, but not so tight as to distort the housings.

I now have about 1/8" slack in each of the 3 cable housings which make up a 1-2 cable assembly, so I can begin synchronization tomorrow. I also took the opportunity to tie up electrical bundles and such, making things neat. The main benefit is that now there are no bends that would add undue friction to throttle/choke cable operation.

I understand what people say about omitting the choke slides, especially in a climate such as California where the ticklers are all you really need. I also appreciate the benefits of a throttle with one cable for each slide. My bevel Ducati twins respond well to that upgrade.

Best regards,
Ken
 
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May 22, 2004
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Mate ~ laying cables is like good music and water.. it flows ~
(NOT ~ jagged!!!)

It is essentially flowing.. gentle curves!!

Plus~ of course ~ good cable quality is important ~ Nylon lined works ~good stuff.
 
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