Marc has been kind enough to give me a tip which I have been wanting for 2 years: how to incrementally lean out my FI mechanically, without a computer. I asked around for a 310/250 injector thinking they would flow less and I could just swap out injectors, like jets, that's real attractive to me. But Marc's tip above is even better: leaning out the entire system by 'tricking" it with an altered position on the TPS. My question: has anyone manually changed the TPS mechanics, under the little cover on the left side? On the butterfly drum, there appears to be a plastic cap with the magnets embedded that maybe slips onto the drum, maybe that plastic cap slips off and then can be slipped back on at a different position?
You are on the right path OHR. Unfortunately it looks like that TPS is not slotted for adjustment, probably because of that plastic pin on right. Your idea on the plasic cap is solid but I would urge you to PROCEED WITH CAUTION!! My experience has been that those kind of parts are not available as replacement spares, and damaging one beyound use could result in the need to purchase a whole throttle body. That plastic pin appears to be a intake air temp sensor, or is there a separate one of those in the airbox/airboot? You may have options there, too, by making the bike think the air is warmer than it really is , equalling a linear leaning.
I have already buttoned it back up, and will think about it, I am pretty sure I will not try and pry that plastic ring off of the butterfly drum. I also think that the plastic pin that inserts into the TB is the air temp, and the part at the front of the assembly may be the air density measurement piece, it has to be lined up as well as the plastic pin, thus removing the ability of using the housing as the rotatable adjuster. I have noticed that I got better gas mileage this past summer when it was 90+ degrees, and on a trail ride the other day in the 50-60s, I got about 28 mpg and almost lost my lunch! What if I pipe some exhaust air into the airbox?
It will run richer because you are displacing some oxygen with spent gasses which will not be combustable. By adding a resistor in-line with the wiring for the IAT sensor, the ECM will see that as a warmer temperature than it really is and will lean the motor in a linear fashion. It is harder to do than tweakin a TPS but looks like the best option for a non-computer tweak of the EFI. It would involve testing the resistance of the sensor at 80deg, 60deg, 40deg etc and duplicating the difference between a temperature step in resistance, with a resistor from radioshack or some source.
That just MIGHT be within my technical capabilities, although the amount of patience it would take is probably outside my limit....
