Installing An Internal Throttle
This isn’t a difficult one but it takes slow time and effort. I handled this in two phases. First I cut the bars and drilled them, even taped the holes. Then I sent the bar to powder. Finally the assembly occurred. There’s something about an internal throttle assembly that’s bothersome. It’s a delicate operation that you don’t want to mess up. Here are some considerations:
You don’t want to break a throttle cable on the road. Nasty breakdown.
You don’t want to snag a throttle anytime and have the throttle catch wide open.
You don’t want to cut the internal throttle cable too long or two short. One is a pain, the other makes you dig for another cable.
You don’t want to cut the exterior housing too long or short. Same reasons as above.
You need to test the length of the cable against the swing of the bars. This can’t be tested too often.
Make sure the cable doesn’t snag or kink on any obstruction.
With those rules in mind I went to work. These rules apply to any throttle cable application, but generally you don’t need to cut and size cables. This particular internal throttle came from:
First I read the directions, reviewed the technical drawing and went
looking for cables to mess with. I knew chances were that I’d screw up at least one cable, so I found an old set of Mikuni push pull cables. I could use either one.
3/32 and 1/16 Allen keys
Okay, before the bars were shipped off to powder coat I started the process. Here’s how the MotoXcycle instructions read: Position and
loosely fasten all controls and housings in order onto 1-inch o.d. bar
ends. Do not forget to include grip length. Note: any extra length of bar
to be removed. Length may vary depending on parts selected. Squarely cut bar ends to size if necessary.
Not sure I understand all that? I narrowed my bars on either side 2 inches, because I could and the lightness of the handling allowed me
to have narrow lane-splitting bars. Other than that the only distance you can cut your bars is 4 inches for the internal system. However, there can be no bends immediately after the 4-inch cut or the system
can’t slide into the bar.
Here’s step two according to MotoXcycle: After bar ends are cut to
size, measure 4 inches in from the end of the bar on the throttle side only, mark off your cut line. Measure it again and then make your cut
as squarely as possible from the throttle side bar end only. This will allow space for the internal throttle assembly.
This was exactly correct and I followed it to the letter. Next: On the
throttle side of the handlebar measure 1 7/16-inch in from the bar end
and center punch the bar. Drill completely and squarely through the
tubing with a #21 drill bit. Tap the holes with a 10-32 tap. (Shim
included for thin wall bars must also be drilled where required.)
This is cool, except for a couple of items. It’s difficult to drill squarely
through tubing. I even have a tubing cradle for drilling round stock. I gave it my best shot. The shim is to be used if your bars are thinner wall than some others. I needed the shim.
Step four is next: Choose a routing path for the throttle cable. (If wire type cable is used, lightly solder cable at throttle end to avoid fraying) Seat outer cable housing in the cable button with 1/16 Allen key. Tighten setscrew in the button to secure (not crush) cable housing. Extend cable wire into puller. Tighten setscrew on puller to bite cable tightly. Push both parts back into the handlebar until the groove in the cable button aligns underneath the tapped 10-32 screw holes in the
bar end. Install screws and tighten down, making certain they’ve entered the retaining groove in the cable button.
Okay, this is all fine except for a couple of items. Routing is critical. I bored a couple of ? inch holes under the bars in the center then beveled and emery sanded the path for the least resistance and wear and tear on the cable housing. Then I sent the bars to the powder coater for a weird copper patina finish. I wanted everything on the bike to look like bare metal.
Here’s the cable button. I’m still not sure if I tightened this setscrew too much. I’ll check it soon.
When the bars returned from the powder master and I was ready to install them, then I set them in the Custom Cycle Engineering traditional dog bone risers and started to figure the length of cable, routing, position and adjustment. This internal throttle system is cool
with needle bearings that will last forever, but there’s also no throttle cable adjustment, so you need to work one into the cable housing or at the carburetor. It’s not a bad notion to set it in the center of the adjustment to allow you some flexibility. Although, I believe I set it at the shortest length.
Here’s a Mikuni Carb cable end.
I measured the length and played with the way the throttle cable would
turn and fit into the Rivera guide for Mikuni carbs. They developed a system, guides and throttle wheel to allow a Mikuni (42 mm) to be used on Shovelheads without interfering with the crossover oil line between the heads.