billyfields
New member
to protect the innocent I will simply say that .. this is for a friend.. here are the facts briefly stated.
the bike: a 99 R1100R with under 30k miles..
the lead up: the owner tried to do some mods (install a clock) on the instrument cluster and smelled smoke.. stopped what he was doing (back track the mods) and then took the bike for a spin to make sure it was ok.. after a few miles the engine quit.. the bike was towed back to his garage.
the examination: the only damage he could find was the instrument cluster harness (under the tank, connector to the right of the stearing column).. several of the wires had overheated and melted the insulation.. he figured he had shorted something accidentally.. figured the best thing was to completely replace the harness but but after two separate attempts (two incorrect harnesses sent) he instead decided to see if he could repair the damage himself. He carefully disassembled the harness and repaired the damaged wires.. don't ask me which ones I don't know..
Puts it all back together and the bike won't start. All systems "normal" - lights etc. The engine turns but it won't fire. He finds that there is no spark. There is power to the injectors. So he sends out the "Motronic" to a local authorized dealer. The dealer give it a clean bill of health. Finally he (friend) changes the coil as there are some cracks in the epoxy sealant on the bottom of the unit. Still no spark.
Anonymous fellow calls friend (me, mr. electrical engineer) in to have a look and I spent a few hours looking over the wiring diagrams and checking out voltages ... so here is what we have..
The coil has two wires going to it.. green and black.. green is hot and goes directly back to the ignition key (I measure 12 V at the coil when the key is on so coil has got power - BTW "kill switch" is good and "sidestand is up"!). The black lead on the coil shows as going straight to the Motronic unit. When I measure from the black lead at the coil (coil disconnected) to Motronic I get 90 ohms R to ground when the ignition is on and open (infinite resistance) when the ignition is off.
I assume that the Motronic does the same thing as the old mechanical points did .. open and close to ground.. closing completes the circuit loading the coil with current and then flipping open shunts the current through the plugs to ground to make spark. So measuring 90 ohms from the coil to the Motronic unit is presumably what the Motronic unit does when it is "closed" to ground. 90 Ohms sounds a bit high?
In any case the dealer states that Motronic is good.
Oh and my friend also replaced the Hall sensor..
So my conclusion is this.. either a) the Motronic is faulty (despite what the dealer says) or b) the Motronic is not ÔÇ£sparkingÔÇØ because some other sensor is reporting a no-op value (remember that we have checked the Hall sensor already) or c) we are missing someting completely here..
Any and all suggestions, thoughts or comments welcome..
the bike: a 99 R1100R with under 30k miles..
the lead up: the owner tried to do some mods (install a clock) on the instrument cluster and smelled smoke.. stopped what he was doing (back track the mods) and then took the bike for a spin to make sure it was ok.. after a few miles the engine quit.. the bike was towed back to his garage.
the examination: the only damage he could find was the instrument cluster harness (under the tank, connector to the right of the stearing column).. several of the wires had overheated and melted the insulation.. he figured he had shorted something accidentally.. figured the best thing was to completely replace the harness but but after two separate attempts (two incorrect harnesses sent) he instead decided to see if he could repair the damage himself. He carefully disassembled the harness and repaired the damaged wires.. don't ask me which ones I don't know..
Puts it all back together and the bike won't start. All systems "normal" - lights etc. The engine turns but it won't fire. He finds that there is no spark. There is power to the injectors. So he sends out the "Motronic" to a local authorized dealer. The dealer give it a clean bill of health. Finally he (friend) changes the coil as there are some cracks in the epoxy sealant on the bottom of the unit. Still no spark.
Anonymous fellow calls friend (me, mr. electrical engineer) in to have a look and I spent a few hours looking over the wiring diagrams and checking out voltages ... so here is what we have..
The coil has two wires going to it.. green and black.. green is hot and goes directly back to the ignition key (I measure 12 V at the coil when the key is on so coil has got power - BTW "kill switch" is good and "sidestand is up"!). The black lead on the coil shows as going straight to the Motronic unit. When I measure from the black lead at the coil (coil disconnected) to Motronic I get 90 ohms R to ground when the ignition is on and open (infinite resistance) when the ignition is off.
I assume that the Motronic does the same thing as the old mechanical points did .. open and close to ground.. closing completes the circuit loading the coil with current and then flipping open shunts the current through the plugs to ground to make spark. So measuring 90 ohms from the coil to the Motronic unit is presumably what the Motronic unit does when it is "closed" to ground. 90 Ohms sounds a bit high?
In any case the dealer states that Motronic is good.
Oh and my friend also replaced the Hall sensor..
So my conclusion is this.. either a) the Motronic is faulty (despite what the dealer says) or b) the Motronic is not ÔÇ£sparkingÔÇØ because some other sensor is reporting a no-op value (remember that we have checked the Hall sensor already) or c) we are missing someting completely here..
Any and all suggestions, thoughts or comments welcome..
