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Background Info and Personal Notes
Variable ignition timing has been important in getting the most out of every gasoline vehicle's engine since the Ford Model 'T'. Early cars had a lever on the steering column to manipulate the timing manually. Modern fuel injected engines employ a computer chip to calculate and adjust the timing.
I initially installed a VOES system for my Mikuni HSR42 aftermarket carb. But over the first year, I noticed that many times the VOES was not advancing the ignition timing when I thought it should have. I never quite knew when my bike would act like a lion or a kitten. So when I upgraded to a Genesis, "Big Air", 48mm carb from PSIPower, Inc, I decided it was a good time to get my TPS back.
Since the Genesis did not provide any place to adapt an on-board TPS bracket, a stand-alone TPS module was my only option. PSIPower offers a stand-alone TPS module (PSI Genesis Big Air Accessories part# 05-009). And one big plus this unit offers is its ability to work with any carburetor. However, as of the date this article was published, their TPS module cost roughly $150. Plus, their unit uses an additional throttle cable -- either the 'push cable' or a 'splitter cable'.
Money aside, this last requirement was a deal breaker for me. I just wasn't interested in re-installing the archaeic 'push cable' that I had removed some years before.
In the end, I decided to build my own TPS module -- one that would incorporate the TPS from my stock carb, not require the throttle's 'push cable,' and would fit in the space under the tank. This article describes how I did this.
Warning: This project is among the most time consuming and exacting of any I have done on my bike. Considering the relatively small, seat-of-the-pants performance improvement it makes, most others would likely prefer to spent their time in other improvements. I am happy with my result, and would do it over again, but then, I enjoy this kind of thing.
Angle Grinder --with cutoff wheel and grinding wheel
Electric drill (minimum) --or drill press, or machine lathe
Bench vise -- or other means to bend heavy gauge sheet metal
Pliers --for bending sheet metal, and general use
General hand tool set --screwdrivers, allen wrenches, file/s, punch, measure, etc.
Tin (sheet metal) snips --or nibbler or plasma cutter
Sandpaper --in the following grits: 50, 100, 220
Dremel, rotary type tools:
- Dremel motor unit, or equivalent
- Small diameter, straight-shaft, diamond cutter
- Sanding drum
- Cutoff wheel
4-40 tap --used to thread the set-screw hole in the pulley.
0.09" drill-bit --used to drill the set-screw hole in the pulley.
2" x 2" x 1/4" mild steel plate (or nylon) --for making the pulley system.
2" segment of a 1/2" mild steel dowel --for the axle.
Brass/bronze round stock or bushings --This will be used to make axle bushings.
Lexan, polycarbonate, plexiglass sheet --At least 4.25" x 3.5" x 0.93". This will be for building the plates that hold the axle/pulleys in place.
8-24 x 3/4" Stand-offs --Quantity 4, for making the framework.
8-24 x 1/2" Screws --Quantity 8, for holding the plates together. I used stainless steel ones.
Thick gasket material --I used pieces of an old inner tube.
Sheet metal --Approximately 24 gauge, at least 6" x 3.5", for making spacers for the TPSensor mount and the dust cover.
6-32 x 2" Screws --Quantity 2, for mounting the TPSensor to the plates. I used stainless ones.
6-32 Washers --Quantity 2, for mounting the TPSensor to the plates. I used stainless ones.
6-32 Nuts --Quantity 2, for mounting the TPSensor to the plates. I used stainless nylock ones.
4-40 Screw --Quantity 1, for use as a set-screw to hold the pulley to the axle.