TBR7 fuel gauge acting like a tach ..

[Bill Hilly]

I have been noticing my fuel gauge acting funny for a while, and thought it was more motion related, but never really gave it much thought, but today, I went on a good long ride, and was keeping a closer eye on it, and realize that it's reading full at higher RPM. I think it has probably been acting like that since I had the tank off to port the head. I had a sudden chugging miss at anything above low midrange about a week, and a half ago, and thought it may have been coil, or CDI, or even some water in the gas. Jerry suggested it may have been the coil not grounding itself good enough. The coil also had some dry, or nearly dry mud on it, Anyway, I cleaned the mud off, and scraped a little paint off from around the coil bolts, and unplugged, and checked the wiring connectors down by the battery, and then I put gently put the tank back on, so as not to slosh the gas around, and then I drained some gas out of it in the reserve position, been I figured water, if present would be on the bottom. My probably went away, and the bike's been running great, but now I'm wondering if the trouble could have been related to whatever is causing the fuel gauge to read full at higher RPM. I ordered a new coil, and CDI, but the CDI hasn't came yet. I will also mention that I have one of those cheap, inductive tachs that just use a wire that you wrap around the coil wire. I've had it for a good while though, and was using it long before the fuel gauge issue. What do you think is causing RPMs to make the gauge read high?

[flopsweat]

This is a total guess, but could it be that the tach wiring is too close to the fuel gauge wiring? I know if wires are running in parallel next to each other that the magnetic field that naturally develops around the wire can affect the next wire over (through capacitive inductance). This is common in high voltage applications, and is often fixed by simply passing the wires across each other at 90deg angles instead of alongside each other. That, specifically, might not be feasible, but maybe just separating the wires a bit might help?

[Bill Hilly]

Originally Posted by flopsweat

This is a total guess, but could it be that the tach wiring is too close to the fuel gauge wiring? I know if wires are running in parallel next to each other that the magnetic field that naturally develops around the wire can affect the next wire over (through capacitive inductance). This is common in high voltage applications, and is often fixed by simply passing the wires across each other at 90deg angles instead of alongside each other. That, specifically, might not be feasible, but maybe just separating the wires a bit might help?

I figured I would go undo the tach wire, and after I did, I started it up, and the fuel gauge was reading below empty, even when I revved it up . I already had my shorts on, so I didn't ride it, but I'm pretty sure that took care of it. When I first installed the tach, I just ran the wire down to that thin rod bracket that runs from one tank fairing to the other, and taped the wire to the rod with a wrap of Gorilla tape, but after I took the tank off for the first time, I routed it differently, and neater, and then after I hooked it back up after getting the midrange chug out of it, I routed even neater, which was probably a mistake. There is a wire loop on my frame up by the neck, and I ran the tach wire through it, and it was snug pulling it through, but it didn't tear the insulation. I just left it unhooked for now, till I ride it again, and then, I will probably try taping it to the tank fairing rod, like it used to be. Here is a picture of how it is now, running through the wire loop on the frame, but I do have it unhooked from the plug wire now. I just tied the end onto the reflector on the fork for now to keep it out of the way http://
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