A 2004 Yamaha R1 road bike that had a mild tune from us a good while ago passed back through the workshop recently, and hiding behind its bodywork is a salutary lesson for us all. The owner originally was going to sell it minus all its goodies, so got the side cutters out and started chopping… then decided he was going to keep it, wanted everything put back on but found the bike was now riddled with faults and problems. There are two issues here; firstly, wiring harnesses do deteriorate with age so while the bike may look immaculate the loom could be an utter disaster and you’d never know (until the faults start) that the actual conductivity of the wire itself has become so poor.
This is especially a problem for fuel injected bikes because they rely on minute changes of voltage to affect the sensors. This R1 had a Translogic quickshifter that’d been chopped out plus the ignition side of its Power Commander wired into the speed sensor, taking out the speedo completely; we had to unwrap the entire loom and essentially re-wire whole sections of it.
Which brings us to the second issue; if you’re going to fit aftermarket goodies when (if) you come to take them off be extra careful. And, if you have an older bike you want to update be aware that the wiring harness may not be on your side. It’s often overlooked simply because it can’t be seen, but even a tidy-looking loom can cause a whole load of grief