What is in the speedometer? Switch??

[Revvy Kevvy]

I am rebuilding the instrument clusters now, taco and speedometer.

I found some nice new surrounds so I cut them to size.

In the speedometer I find a switch, does anybody know what this switch is for? The light is a seperate circuit and there is like a switch shown on the schematic but for the life of me I cannot imagine why a switch would be in this place?? What does it do?

Schematic shows it as a switch, there are two wires coming out but why would a switch be there...see pictures if you dont know what I am talking about.

 

[Revvy Kevvy]

Just to close this, the switch inside the speedometer is a self cancelling turn indicator. It apparently needs the speed to understand how the bike will lean into a corner and will reset itself. I dont really get it past that. Maybe it has some mercury switch in there but how it compensates for the lean I have no idea. Sounds like something thats gunna cause problems .... I sort of think of it like the turn and slip on a cessna 172 except thats operated by vacuum...

Maybe I thought the turn indicators dont work when the bike is upright (not in a lean for a turn) but...nope, the indicators work just fine when the bike is on its side stand. Who knows how the idea works.

 

[CaptChrome]

Maybe I thought the turn indicators dont work when the bike is upright (not in a lean for a turn) but...nope, the indicators work just fine when the bike is on its side stand. Who knows how the idea works.

Yes, the reed switch is used to send a speed signal to the self-cancelling unit. The faster the speedo cable spins, the faster a magnet spins next to the reed switch and the more electrical pulses are sent to the self-cancelling unit. It does not use lean angle at all as an input, but instead the self-cancelling unit uses the speed signal and elapsed time at speed to determine when to cancel the turn signals.

I don't know exactly how the self-cancelling unit does this, but when I converted all of my lighting to LED, I removed the self-cancelling unit and have been templed to crack it open and have a look inside to figure out how it works. Maybe with I get done with all of the other projects (i.e. never).

 

[Revvy Kevvy]

I suprisingly complex system to tell the bike the indicator is still running. I guess its much more complex to manage than a car since so real steering wheel concept exists. I tried tipping the bike over with the indicator on once I worked out what it was and it did not self cancel so I was somewhat perplexed how it worked thanks for clearing it up.

Today I complete rebuilding the front forks, replace the bearings on the front wheels, finish rebuilding the front brake system and have a beer when its all done.

I bought a replacement light bulb in LED for every light on the bike when I was in china and the project will be to change them all once this bike is rebuilt and reregistered to run on the road. Is it just so easy as change them or do I have to put loads in the system to compensate. I think the turning indictors need a load to bend the bi-metalic strip that I suppose is in the click clak box...TBH I had not got even close to thinking about this part of the project except that maybe it needed a load for the click clack box at I recall the old ones used a bi-metalic strip that disconnected when hot.

 

[Revvy Kevvy]

Yes, the reed switch is used to send a speed signal to the self-cancelling unit. The faster the speedo cable spins, the faster a magnet spins next to the reed switch and the more electrical pulses are sent to the self-cancelling unit. It does not use lean angle at all as an input, but instead the self-cancelling unit uses the speed signal and elapsed time at speed to determine when to cancel the turn signals.

I don't know exactly how the self-cancelling unit does this, but when I converted all of my lighting to LED, I removed the self-cancelling unit and have been templed to crack it open and have a look inside to figure out how it works. Maybe with I get done with all of the other projects (i.e. never).

\do you mind if I ask where is the actual turn indicator killer? On the diagram is shows it near the condensors, but I dont find it there. Its not in the actual indicator switch on the left handlebars. I did not see anything inside the headlight that looked like one....where did they hide this little unit? What does it look like, a square box with lots of wires coming out of it is my guess but its well hidden...

 

[CaptChrome]

where is the actual turn indicator killer?

On my 1981 XS400H, it is below the rear end of the fuel tank, beneath the frame cross-member. It looks like this:

I bought a replacement light bulb in LED for every light on the bike when I was in china and the project will be to change them all once this bike is rebuilt and reregistered to run on the road

Good idea. Just be aware that you will probably have to modify the circuit at the pilot bulb with some blocking diodes, remove the auto-cancelling relay and put a jumper in its place and use a new flasher relay to make this work. There is some info on here about these mods, but if you get to that point and are having trouble, help is just a post away!