Fabricating a TPS Driver

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Written by Randy Fox (randysgym)   
Thursday, 27 August 2009

Fabricating a Mounting Bracket

Designing and building the bracket took as long as building the TPS Driver itself. As small as the unit is, I still found it challenging finding a location near the carb that was spacious enough, yet also allowed a natural flow for the throttle cables. In the end, I found just enough room above the intake manifold, just forward of the upper motor mount, and behind the front rocker cover. See photo below, TPS module highlighted in yellow.

 

yamaha road star, tps driver, throttle position sensor, bracket

 

In retrospect, it might have been a better option to mount the unit between the upper motor mount and the front rocker cover -- transverse (sitting sideways). If this option would have worked out as well it looks, it would allow a more graceful throttle cable run from the TPS to the carb; mine has no room to spare.

My bracket places the TPS module as far forward as possible, and routes the throttle cable inboard of my Nemesis aftermarket coils. See my final design pattern diagrams below. Each diagram shows the same design; I just split all the info up into 4 drawings to make it easier to digest, hopefully.

 

yamaha road star, tps driver, throttle position sensor, bracket

 

yamaha road star, tps driver, throttle position sensor, bracket

 

yamaha road star, tps driver, throttle position sensor, bracket

 

yamaha road star, tps driver, throttle position sensor, bracket

 

The diagram shows bend lines as blue dash lines. It also indicates the direction and order of each bend via the numbered, red/yellow, arrow-circles. It also shows the approximate location of holes to drill.

The dimensions and angles of your project may differ. Consider this info as a good starting point. Make some paper, and some 26 gauge sheet-metal mock-ups, before finalizing your design to heavy gauge, 16 gauge plate steel.

The basic pattern, glued onto sheet metal should look something like the following photo. Note: this photo is actually of an earlier design.

 

yamaha road star, tps driver, throttle position sensor, bracket

 

Once I cut the pattern cut out, I bent along the dotted lines, and my bracket looked like the photo below.

 

yamaha road star, tps driver, throttle position sensor, bracket

 

yamaha road star, tps driver, throttle position sensor, bracket

 

Note: The above photos show a slightly lesser evolved design from my final design.

From this point, I fit, bent, fit some more, welded, trimmed, and bent some more, until I reached my final design, as given in the diagrams earlier. My bracket looked like the photos below.

 

yamaha road star, tps driver, throttle position sensor, bracket

 

I then reinforced the cable receiver tabs of the bracket via small welds. However, JB Weld epoxy would work equally well. The reinforcing supports are shown in the photos below. (Note: The photos were taken after final paint was applied.)

 

yamaha road star, tps driver, throttle position sensor, bracket

 

yamaha road star, tps driver, throttle position sensor, bracket

 

Finally, I drilled and tapped the upper motor mount on the bike’s frame to receive the 6mm bolts I used. I also replaced the right-side coil bolt with a slightly longer one, to accommodate the thickness of my bracket, mounted at the rear of the coil.

Then I cut a piece of old inner tube to use as a gasket and vibration damper. The rubber piece was doubled over and hole punched to fit under the rear mounting points (on the upper motor mount). See photo below.

 

yamaha road star, tps driver, throttle position sensor, bracket

 
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