Guest Kakugo Posted October 10, 2015 Share Posted October 10, 2015 I have a friend with a the aforementioned Airhead bike who's been having seriour electric troubles since August. To cut a long story short he changed the diode board with a second hand one off eBay because of charging issues. Since then the bike has become... even worse. The starter relay has gone south (signs of a flameout ) , the ground wire coming off the diode board overheats badly and charging has become erratic. A new starter relay somewhat helped things but I told him it will probably melt as well in the not so far future. I personally suspect the problem is still in the diode board: I know BMW had issues with both Wehrle and Bosch ones and some Airhead tech gurus recommend either replacing it with a beefed-up aftermarket one or modifying the original one. But before telling him to fork out the equivalent of US $70 or so for an aftermarket one I want to have confirmation a bad diode board can cause such issues. Thanks. Link to comment
Guest Kakugo Posted October 12, 2015 Share Posted October 12, 2015 I am posting here in case comebody in the future has similar issues. Turns out there are two BMW Service bulletins (12-012-88 and 10-019-93) dealing with this issue which can pop up on all Airheads built from 1980 onwards and equipped with a diode board as part of the charging system. BMW's suggested cure is a mix of modifying the diode board (first bulletin) and adding a ground wire harness (second bulletin). Due to labor and cost of parts relative to these bikes' value, it makes more economic sense buying an aftermarket diode board and harness from Enduralast (the equivalent of $75 plus shipping). Link to comment
lkchris Posted October 16, 2015 Share Posted October 16, 2015 On the R100s and only the R100s the diode board was rubber mounted. The extra grounding harness is required to assure good grounds. Doesn't change if you fit an aftermarket board. It's possible to buy metal mounts to replace the rubber mounts ... at which point you take your chances with vibration. Link to comment
Guest Kakugo Posted October 19, 2015 Share Posted October 19, 2015 On the R100s and only the R100s the diode board was rubber mounted. The extra grounding harness is required to assure good grounds. Doesn't change if you fit an aftermarket board. It's possible to buy metal mounts to replace the rubber mounts ... at which point you take your chances with vibration. Endurlast makes an extra grounding wire harness to go with their diode board. It costs the equivalent of $15, which I already factored into the the $75 price. No idea how much a second-hand genuine BMW wiring harness goes for, but I have the feeling at least twice as much. Link to comment
lkchris Posted October 27, 2015 Share Posted October 27, 2015 They were free back in the day, and I wonder if they ever got a part number put in the system. Link to comment
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