I didn't get the purpose of that thing tho...I TW americani non hanno tachimetri. However the sensor likely provides the pulse once per revolution that is the core of the rev-counter's function. That circuit opens and closes each revolution would indicate it is working properly.
Ahhh hahahaha yeah I got now the joke, in Italian is called differently ^^
Well if that's the purpose it is failing since that's just a speedometer connected to nothing hahahaIt reports all your travels and speeds to the federal government at the FBI and CIA. The FBI monitors everyone in the states and the CIA monitors everyone outside the national borders.
So basically that Speedometer of the TW125 I purchased (just some parts actually, it misses the frame and tires, but rest is complete with engine etc etc) noone knows what the hell it does XDIf it is a mechanical tachometer it functions not unlike your speedometer, only it reports engine revolutions rather than tire revolutions which then becomes an analog for vehicle speed.
Basically a rotating drive feeds into the back of the tach and spins a magnet inducing eddy field in the aluminum disc. In a speedo the part referred to I believe is called the "Speed Cup".
Without a better picture can't tell if you have a more modern impulse tachometer. If so then it functions a little differently: "Two pairs of connections were required, one pair for the supply leads and the other for the pulse pick-up leads. The pulse leads were, in fact, one continuous wire with a loop (forming the primary winding of a transformer) taken around a soft iron core projecting from the rear of the tachometer casing. The advantages of this type of signal pick-up were that there was no break in the ignition wiring, so a break in the tachometer circuit would not affect the ignition; and that there is no direct electrical connection to the ignition from the tachometer circuit.
The secondary of the transformer, inside the tachometer case, was connected to a printed circuit that applied current pulses, originating from the distributor and therefore at a frequency depending on engine speed, to the indicating meter. The internal circuit was fed from the supply leads, one of which was taken to one of the vehicle's existing switched and fused circuits running back to the battery, the other to earth (ground). Of the pulse leads, one was taken to the contact breaker (CB) terminal on the ignition coil, the other to the contact breaker (side) terminal on the distributor. The previously existing CB to distributor wiring was discarded. Note, however, that modern ignition coils, the SW and CB connections are marked' -' and' +' for positive earth systems and '+' and '-' for negative earth systems"
Dear Purple,The main problem with identification is that the speedo is sold as a sealed unit only, and is not meant to be opened up — so there are no schematic diagrams revealing its internals
Two questions — how sure are you that this speedo comes from a TW125 — and are there any electrical connectors from the unidentified component ?
I am just trying to understand what it is and what it does for the bike since it seems to do actually nothing at allSo jannaruto, you definitely have a speedometer, not a tachometer.
And you were teased again about the "cruise control" or "speed sensor" , the box around object in your second photo is the speed cup and aluminum eddy current disc for the speedometer and odometer functions.
Are you just trying to understand it, or repair it?
Does it have a mechanical problem, missing pieces, or an electrical problem?
Review the Service Manual for help. Here is a downloadable copy:TW200 Service Manual - searchable pdf
Well so maybe it is that I assume...“If” its purpose is to send a single pulse every revolution, the only reason I can see for that, is at top speed, it would be able to send a signal to the rest of the bike preventing any further increase
As you have already mentioned, this is rather unlikely on a TW125, which is notoriously underpowered in the first place
Having said that (however), the TW125 has a few tricks up its sleeve that are not found on the TW200 – the carb heater being just one of them
It is entirely possible that this a “speed limiter” for a 125 in your region – the component in question would detect “top speed”, after which, presumably it would “restrict” the bike somehow from going any faster ……