TBR7 Gear position switch/sensor

[bayne05]

Hello, new rider here, been riding/wrenching on my 21 TBR7 for about 2-3 months now. Bought it from a good buddy mostly stock, so as per the nature of the beast (& a tendency to accidentally throw it on the ground), I've had to replace a fair number of parts in that time, though there's only one issue I've had thus far that I haven't been able to find conclusive answers for by scouring here/ tbr7.com. Had the chain pop off about a month back, smashed up my front sprocket case a bit but nothing appeared broken or overly worn on the chain/sprockets so I hadn't thought a whole lot of it to be honest, just rolled it back on, cleaned/lubed, adjusted the slack & kept riding until it popped a second time & broke the chain, I've since replaced the chain/sprockets and the only adverse side effects I've noticed are that the gear indicator reads exclusively 5th gear (whether actually in 5th or not) or completely blank at any given time, and sometimes when starting I need to let off the clutch a little bit for the starter to crank. Hadn't really bothered me until I put on my new zanella speedo yesterday & it just didn't feel complete, after a little digging it seems the best explanation is that there's probably some broken wires in the gear position switch/sensor. I haven't been able to find a working link for a replacement that's verified to work with the TBR7, & while I do have a cheap soldering iron laying around from a couple years of hobbyist experience in electronics repair (controllers, phones, etc.), putting on the digital speedo yesterday was my first time dipping my toes into wiring & I just frankly have no idea what I'm doing :p. Would it be worth trying to take it out & find/solder together the broken wires? Does anyone have a working link for a replacement part lying around? Pics for reference, & big thanks to the people here and at tbr7.com for carrying me through my first handful of repairs/replacements :)
-Bayne

[Thumper]

I am pretty sure the connection grounds the lead going to the gear changer/roller and each wire is grounded separately for each gear position. Wires should be in a circular pattern on the end there, in front of the chain where the thing connects the engine.

You can verify this by removing it and testing (voltmeter set to ohmeter) for continuity with the engine in each gear position (on the exposed posts on the flat round plastic connector... There is a plastic round plate with the wires going into it, or where they used to connect!

You can verify/associate each connection to a gear position using the ohmeter, manually shifting. No key on needed. My guess is that when it is in 3rd gear, for instance, ONE wire would have been connected/grounded to the engine (plastic cap on the engine). So that post on the round thing will be grounded. Note the position on the round plastic thing for each gear.

Then you can try to illuminate each number on the speedo by grounding each wire separately, one by one to figure out which is which. This assumes that these wired aren't 12V. Write down the colors for each gear. Then resolder them in.

Am I making any sense?

I doubt that power is distributed there (but rather, ground is distributed when you shift gears).

[bayne05]

Yeah, that makes sense, I'll give it a shot in a little bit here & update afterwards. Thanks again!

[bayne05]

Originally Posted by bayne05

Yeah, that makes sense, I'll give it a shot in a little bit here & update afterwards. Thanks again!

Welp, turns out I was following the wrong wire down & the sensor was a little lower than I'd thought. Issue made itself clear pretty quickly after I started cutting the sheath off. Probably gonna take a while, but at least it's pretty straightforward what to do from here.

[awander]

If you need an inexpensive replacement for the gear sensor and cable, I found that this one on AliExpress fit my 2023 TBR7 just fine, the only difference was that the cable itself was a few inches shorter on the replacement, but it worked fine.

https://www.aliexpress.us/item/32568...yAdapt=glo2usa

The description (for when the listing disappears), was "1 Set Motorcycle Gear Sensor Shift Position Indicator Lever For Lifan LF150-10B LF125 Zongshen RC200 GY-C2 Irbis Garpia 157Fmi"

Cost was around $4

[Thumper]

Originally Posted by bayne05

Welp, turns out I was following the wrong wire down & the sensor was a little lower than I'd thought. Issue made itself clear pretty quickly after I started cutting the sheath off. Probably gonna take a while, but at least it's pretty straightforward what to do from here.

Did you reconnect those severed wires. It sure looks repairable. The copper sensor pads seem OK. Rewire, cleanup and reinstall should restore the gear position indicator.