Clinic
You CAN do it...
Fabricating a TPS Driver |
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| Written by Randy Fox (randysgym) | |
| Thursday, 27 August 2009 | |
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Page 2 of 10
Background Info and Personal NotesVariable 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.
Tools NeededAngle 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:
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.
Materials Needed2" 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.
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