Fabricating a TPS Driver

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

Fabricating the Framework or Plates

I built my plates from the following:

  • 0.093" thick, clear, Lexan (polycarbonate/plexiglass)
  • 10-24 x 3/4" 'stand-offs'
  • Stainless steel screws

See photos and diagram below.

 

yamaha road star, tps driver, throttle position sensor

 

 

yamaha road star, tps driver, throttle position sensor

 

There were several tricky parts in building the framework:

  • The stand-offs needed to be shortened so that the unit would be as thin as possible.
  • Two of the stand-offs needed to be filed (or milled) to accommodate the swing of the pulley so that the unit could be as narrow and short as possible. See photo below.

 

yamaha road star, tps driver, throttle position sensor

 

The plexiglass plates were drilled for the stand-offs so that the stand-offs were flush with the edges of the plates. Also, the plates were drilled for the axle pivot bushings at a point centered side-to-side.

The next step was to make the axle pivot bushings. I made mine in my mini machine lathe, but you could buy some ready-made bushings through a clock parts supplier, or perhaps an R/C model store. See photos and diagram of mine below.

 

yamaha road star, tps driver, throttle position sensor

 

yamaha road star, tps driver, throttle position sensor

 

Next, the bushings were 'glued' into the plates. The smaller bushing was secured using silicone, high-temp, RTV, gasket maker. I figured using silicone would allow me to easily replace the bushing some day, as needed. See photo below.

 

yamaha road star, tps driver, throttle position sensor

 

The bigger bushing needed stronger glue. I ended up using small amounts of JB Weld, which I hope to be able to file away, should the need arise to replace that bushing.

After the bushings were in, I needed to create a ‘well’ for the Yamaha TPS unit, since I had decided not to make any modifications (cutting, filing, or trimming) to the TPS. Tip: By keeping the Yamaha TPS unit stock, I could do a simple swap-out, in case mine failed at some point down the road.

The ‘well’ I created was built up from the following (in order, from bottom to top):

  • A piece of 26 gauge sheet metal
  • 3 plexiglass layers
  • A piece of rubber inner tube
  • Another piece of 26 gauge sheet metal

The first 4 layers were glued together, and the bottom layer (sheet metal) of the stack was glued to the plate. The top 2 layers (rubber and top sheet metal layer) were left unglued. See photos below.

 

yamaha road star, tps driver, throttle position sensor

 

yamaha road star, tps driver, throttle position sensor

 

yamaha road star, tps driver, throttle position sensor

 

I made the ‘well’ oval shaped for no reason in particular. Once the ‘well’ was glued up, I reduced the overall height a little, to position the Yamaha TPS to the proper depth. To do this, I just sanded off the top plexiglass layer of the ‘well’ until proper depth was achieved.

I secured the Yamaha TPS unit to my plate via 2, long, stainless screws, nyloc nuts, and a couple of washers. I decided to embed the nuts into the ‘well’ so they would be near-flush with the inside of my plate to prevent interference with pulley movement. By fixing the nuts into the plate, I am now able to adjust the stock Yamaha TPS unit by simply loosening the screws, just like it was intended.

To embed the nuts, I first glued my ‘well’ together (as stated above) using JB Weld, being very careful to line up the big holes for the TPS. Next, I carefully drilled 2 shallow holes into the plate, large enough to accommodate the nuts, that were aligned with through-holes I had already drilled to line up with the Yamaha TPS mounting holes. Then I JB-Welded the nuts to the plate, being very careful not to get glue onto the threads or the through-holes. See photo below.

 

yamaha road star, tps driver, throttle position sensor

 

yamaha road star, tps driver, throttle position sensor

 

It may not look pretty, but it’s strong.

 

 
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