88-gl1500, rpm noise, not sure if the bike had the cable upgrade, no blue tape on cable, can't read no. on radio either, trying to swr radio also, should i plug into radio or at splice under seat for a good reading.
Won't make any difference where you splice. Was this radio on the 88 when you bought it or did you fit it and are hearing noise now? If you fitted it and didn't install the fuel pump and alternator filters as well, you will be sure to get interference noise.