Triumph Twins Adjusting the Carburettor Throttle Position Sensor
Having the TPS correctly adjusted is very important as the igniter unit needs the correct "engine load" parameter along with "RPM" and "advance angle" to be able to select the correct amount of ignition advance for any throttle position. The igniter will interpolate between Ignition maps to derive the Ignition angle B.T.D.C. to be applied. If the TPS adjustment is incorrect it will affect your ignition advance and can effect the power delivery and economy of your engine.
If you're the original owner of your Triumph twin and you know the TPS has not been adjusted, DO NOT TOUCH IT, it will have been correctly adjusted by the factory and the paint spot should be aligned and not show a break in the surface. If your TPS is damaged in any way, it can't be replaced on it's own, you will have to buy a complete set of carbs from Triumph or a breakers yard. So be careful........you have been warned.
Before you attempt to adjust the TPS, make sure the carbs are balanced correctly. The tools needed for TPS adjustment are an OHM meter, a small flat blade screwdriver and a TORX security screwdriver or socket attachment.
The first step is to twist the idle adjuster 10 full turns anti-clockwise to ensure the idle adjustment screw isn't interfering with the readings. Then remove the right hand side panel for easier access to the modular connector and part the connector by pushing in the tab on one of the three sides and pulling it apart, this may be achieved more easily by pushing the tab down with the small flat blade screwdriver while pulling each side apart (you could really do with three hands). The connector can be a pain the get at and you may have to ease the wiring loom in that area for access.
Next twist the throttle and let go to ensure the carb butterfly spindle which drives the TPS is in the completely closed position. Slacken the security TORX screws on the TPS slightly, just enough so the TPS can be moved, too loose will effect your readings. Switch on your OHM meter and connect to the blue and yellow wires in the TPS connector, move the TPS to attain the correct reading, nip up the TORX screws and test a couple of times at full throttle and closed throttle. You may have to adjust and test again to finally achieve the correct reading.
The TPS is an analogue potentiometer and is not a precision device so the readings might not be exactly the same each time you open and close the throttle.
TPS readings from a showroom bike are:
Blue & Yellow wires = 4.42K OHMS closed throttle & 1.38K OHMS wide open throttle.
Black & Yellow wires = 0.81k OHMS closed throttle & 3.96k OHMS wide open throttle.
Once you are happy with the readings tighten the TORX screws, but be careful the carb body is very soft and the threads can be stripped very easily. There are no torque settings from Triumph for these screws as the TPS is not supposed to be a user adjustable item. Reconnect the the modular connector to the wiring loom, refit the side panel and twist the idle adjuster screw 9 full turns clockwise, then start the engine and adjust the idle to your preferred setting.
Well done, that's sorted the TPS, now go for an enjoyable ride.