Per
Takegawa's instructions for the CT125 they want you to run the brown RPM/tachometer wire that they included to the pink/blue connection on the ignition coil. The ignition coil is located under the plastics that cover the "spine" of the bike where you have a center carrier mounted.
View attachment 7970
I would recommend downloading the Japanese instructions PDF from that link, then upload it to
Google Translate for documents to do a rough machine translation of it to English.
Once you have it set up I would be curious to hear your thoughts on the Super Multi TFT Meter. I have both that and an OPMID on hand and haven't gotten around to deciding on or installing either.
One of my initial concerns for the Takegawa meter was units of measure. I contacted Takegawa directly about this and they said it cannot be changed. I contacted Webike about it and they wrote "Changes are not allowed in Japan and are not mentioned in the instruction manual" but then said it could be changed and provided the instructions to switch between kilometers and miles. The only other negative impression I had of it is that the analog tachometer has much more range than what's usable on the CT125's engine. The integrated air fuel ratio display seemed like a really nice feature if you wanted to add a bung to the exhaust, install an o2 sensor, and wire that up.