'54-59 OHV Handlebars

[VintageTwin]

Here's some of (VT 25-0661). The VT speedsters are the exact same as OE. I placed them on top of OE buckhorn (with cables run) to show the different contours. I like buckhorn for rigid frames, but speedster pull back enough. I have them on a '59 swing arm.

[VintageTwin]

three more

[VintageTwin]

And two

[VintageTwin]

Happy Jack. All the internals fit with only a little round and flat filing.
The drilling of the screw holes left slag and the milling of the slot left an uneven surface where the bottom roller tracks. Look at the bottom of the three photos. I taped OE handlebars above the re-pop ones. Look at the side track of the slot in the re-pops. See the uneven wavy surface? This would cause the throttle to bind half-way and only push the wire control out about 1/2". Both spirals should push the control wire a distance of 1-1/4". The slot sides need to flat-filed. Carefully. Don't take-off more material than is necessary to allow the throttle to operate smoothly.
Run the coil-plug into the handlebar backwards at first (this way you'll have a coil-handle to hold on to and be able to push and pull the coil out when and if, it gets stuck), and be sure the plug will clear any inner drill-windings, and be able to be positioned, centered, under the screw hole for the tapered plug screw to seat.

[VintageTwin]

When you try the throttle action and it binds, leave the throttle in the bound position and remove the spiral. This way you know where the bind spot is and the plunger can be removed and the area flat filed some more. To me, handlebar work is more akin to gun & rifle maintenance.
The handlebar plug screw has a wide slot. These plugs will be destroyed by a regular screwdriver. Make a special screwdriver for this purpose by grinding the tip off one until it's fat.
Once the plunger is installed, loosen, then re-tighten the plunger Allen-set screw, so the control wire can twist and relieve any binding within the control coil.

[VintageTwin]

The wide slotted handlebar plug screw that holds the coil plug in position. The plug screw in the handlebar has a burred slot from using the "wrong" tool for the job.