Hand throttle - how I did it

I decided to fit a hand throttle and my first attempt looked like this.

Yes it is that simple, the string is looped around the throttle inner cable where it joins the throttle pedal upper arm. Simply pull and rev 'er up.  The string follows a fairly unobscured route so will not chafe against too much but there is a bit of wiring harness that it contactsbut don't panic,,,,,,,,,you shall see why later.

But there is a drawback.  You will need to find a way to hold the string in the position that holds the idle you want.  Amazingly very little is needed to kick the revs to 1200.

But then that was just a prototype.

What I am going to do is fit a proper choke cable, you can get them for about a fiver on eBay.  One of the threads on the forum actually put a hand throttle cable through the switch hole as in the picture above.  I have chosen to use a choke cable as it is free running so will not put any pressure on the switch housing which can pull the switches out as they are a combi unit and easily come out forwards leaving the connectors in another housing behind.  When the amount of throttle is found you twist and lock the knob.  Enough of that.  After some puzzling I found the PERFECT spot for a choke cable which is accessible from the rear too though I will be using two nuts so I can tighten it up from the front.  More of that when I get to that stage.  You can see the spot here.

Behind that spot is an unfettered direct line route to the top of the throttle arm.  You could just route your string through a hole just there and have knots in it to hold it in position.

This is the end coupling on the choke cable.

I shortened it as it was about 1.5m long.  Also it is a solid inner wire that makes it easier to cut, stranded inner cables need soldering first to stop fraying when cut.

The next step is to make a coupling to go on the actual throttle cable so I can link the choke cable to it. I realised it needs to attach to the cable behind the arm of the throttle pedal because otherwise I will be fighting the pedal's return spring as well as the throttle body's spring.

I made this - apologies for the quality of the picture; I cannot retake it as the thing is now on the cable and apologies for the Heath Robinson quality too.

When I came to fit the coupling the blob on the end of the throttle cable seemed bigger than the 12mm I had measured so I had to open the hole and slightly deform what you see by spreading the thing; it now has a more rounded shape.

The bolt on it is an M5. I threaded the coupling for that and put in a small spacer tube as I wanted something to stop whatever I attach to be rubbing on screw thread.  

The inner cable is 2mm so I made the slot 3mm.  Also fitting this means that the adjustment at the throttle body needs changing; it is only a millimetre or so but it does raise the revs.

At this stage I attached my pull string and discovered a few home truths.  Most important is that the route taken via the switch hole means that there will be a lot of rubbing on an underdash wiring harness - in two places.  That applies to what I thought was the perfect place too; in fact it was the perfect place from the point of view of use and fitment in the dash but as I have couplings that will contact the harness and cut it to shreds both are out of the question.  The problem is that I have to allow some distance between couplings for slack as I will be connecting the new coupling to the coupling on the choke cable by something flexible, probably that string!  That puts the choke cable coupling right there on the wires.  Annoying. Also annoying was the clevis pin, the cable slipped out of my hand and the pin flew off into the chassis by the A post never to be seen again!.

I now need to find a new place to mount the actual pull knob and to be honest the direct line of sight puts the knob much much lower, in fact about a foot below the original perfect spot.  It also clears all obstacles too, right at the bottom of the dash.

It looks like I may have to make a special bracket to hold the choke unit in place.

TBC.................