100 Choke Modification

[TodE]

Has anybody done or know of somebody that has modified or replaced the choke assembly on a 100-4? It does not work very well. For those who have not seem one, basicaly you have the cable that pulls up on a "stirup" setup that then pulls the choke levers up.

The problem is that, sometimes it will only pull up one choke lever, if any at all. So to adjust the choke you need to pull up on the choke levers (both), pull down on the choke cable, and tighten a tiny screw that holds the choke cable in place. All in a very tight spot.

There has to be a better way!!

 

[andrewss]

I have just finished a modification for a client for the very same problem on a BN1 100/4. I will upload some photos tonight and a description of the solution I came up with.

Andrew

 

[MikeAH100M]

I am having the same problem. I addition, it is difficult to get the choke to stay in a set position. Pictures would be very helpful.

 

[andrewss]

The pictures probably don't do the design justice but the drawing makes things a little clearer. First of all you need to go to a bicycle shop and buy a brake cable with a nipple and an adjuster (which fits normally on the brake lever and allows you to adjust the cable). The brake cable has a soldered nipple that you will use instead of the awkward screw that normally allows you to adjust the choke cable. The brake cable is the same size as choke inner cable so slips in place of the original cable. You need to solder the cable at the choke Knob after having heated the old cable up with a small blow torch so you can change it. Make sure that the cable length (when you cut and solder) allows you to adjust the tension of the cable. I made a 'V' shaped bracket (bought from a hardware store) to which I added a nut and bolt (filed flat on the top side) and then drilled a pilot hole for the cable (2/3mm) followed by a second (6mm) in the same hole but only half the depth to accept the adjuster. The inverted 'V' bracket for the two choke arms is made from aluminium with small screws located to attach the arms. None of this required welding although this is an option..

 

[steveg]

Another method would be to adapt your setup to a BJ8-style two-cable solution. I did that with teflon-lined bicycle cable sheaths and setscrews at the cable housing ends to hold everything tightly in place and it positively opens and fully closes the two carbs. I believe a setup like this deals positively with one carb choke lever which was sticker than the other.
See:
https://www.pbase.com/stevegerow/image/109657958
and succeeding photos.

 

[BLU_HLY]

The 'wishbone' wire was removed and replaced with a clevis arrangement that allows the choke to move more easily.