Cook1e
Registered user
The bike (R1150GS, 2001, ABS removed and Power Commander III Wideband fitted/dynoed years ago) has been laid up since about November, when I put it up on the bench to replace the rear brake light switch. The rusty subframe caught my attention and I've had the arse-end of the bike stripped down to de-rust and re-paint it.
During the winter months, progress was slow and I charged the battery from time-to-time and started the engine a couple of times. Nothing electrical was disturbed apart from removing the tank and the rear lights wiring. The bike had been running perfectly prior to the lay-up.
A few days ago, I finished the work, re-assembled everything and started the bike on the bench. All seemed fine, so I backed it out of the garage, put it on the side-stand and went to get my boots & helmet etc. for a test-ride.
I got my leg over and tried to start the bike. Nothing happened apart from the normal fuel-pump prime and just a click when I pressed the starter, but then the rev-counter went up to about 2,000 rpm and stayed there. Same again when I switched off and tried again and I noticed that the rev-counter went to about 2,500 with the starter button pressed and returned to 2,000 when the button was released. The clock also reset to 00:00.
Copious foul language ensued, and I removed my riding gear, pushed the bike back onto the bench, put the battery on charge and went indoors for a drink and a think.
The following morning, I tried again and the bike started reluctantly, so I went for a ride. Although it had revved freely in neutral, under load it was surging really badly (I was nearly spat off!), as if the ignition was being cut for a split-second every few seconds when the throttle was opened. Nothing out of the ordinary on the dashboard though, rev-counter etc. reading normally.
Back to the bench, where I checked the obvious:
- throttle cable seating
- plugs & leads OK
- changed the fuel for fresh
- side-stand and clutch switches OK
- fuel pump priming and running normally
- fuel tank electrical connector OK
- removed, cleaned, refitted and re-balanced the brass mixture screws (these were fairly shitty, so I had high hopes)
I also fitted the Power Commmander mixture gauge (analogue dial which connects to the PC module and displays air:fuel ratio), in the hope this would provide diagnostic information and went for another test-ride.
Still the same.
The PC gauge flicked between a rich 11%-ish (engine still cold of course) and 18% (maximum lean) when the surging happened.
Searching this forum, I learned that a dodgy TPS may cause these symptoms, so I checked the voltage (pin 1 to pin 4 and pin 1 to frame earth). It was all over the place, between 0 and nearly 5 volts! Aha! Problem solved, I thought.
Nope.
Having disconnected the Motronic connector to get at the pins and stripped the tape off parts of the wiring loom to check the connectors and those supposedly trouble-prone bundled earth connectors, everything checked out fine and testing the resistance of the TPS at idle & full throttle, everything checked out fine. I did notice that pin 4 of the TPS doesn't go to earth as I would have guessed, but to pin 22 of the Motronic, along with the 'earthy' ends of the oil and air-temparuture sensors (circuit snip attached below).
So all I can conclude is that, during the failed start, where the engine didn't turn over, but the rev-counter indicated 2,000 rpm, the Motronic fried itself, resulting in the weird voltage readings on the TPS. I don't know why this happened, but I'm going to check the battery, earth and starter connections as the symptoms were like a flat battery, except it had started OK 10 minutes previously.
All comments and questions welcome - in the absence of other plausible explanations, I'm going to phone MotorWorks tomorrow to price up a replacement Motronic
During the winter months, progress was slow and I charged the battery from time-to-time and started the engine a couple of times. Nothing electrical was disturbed apart from removing the tank and the rear lights wiring. The bike had been running perfectly prior to the lay-up.
A few days ago, I finished the work, re-assembled everything and started the bike on the bench. All seemed fine, so I backed it out of the garage, put it on the side-stand and went to get my boots & helmet etc. for a test-ride.
I got my leg over and tried to start the bike. Nothing happened apart from the normal fuel-pump prime and just a click when I pressed the starter, but then the rev-counter went up to about 2,000 rpm and stayed there. Same again when I switched off and tried again and I noticed that the rev-counter went to about 2,500 with the starter button pressed and returned to 2,000 when the button was released. The clock also reset to 00:00.
Copious foul language ensued, and I removed my riding gear, pushed the bike back onto the bench, put the battery on charge and went indoors for a drink and a think.
The following morning, I tried again and the bike started reluctantly, so I went for a ride. Although it had revved freely in neutral, under load it was surging really badly (I was nearly spat off!), as if the ignition was being cut for a split-second every few seconds when the throttle was opened. Nothing out of the ordinary on the dashboard though, rev-counter etc. reading normally.
Back to the bench, where I checked the obvious:
- throttle cable seating
- plugs & leads OK
- changed the fuel for fresh
- side-stand and clutch switches OK
- fuel pump priming and running normally
- fuel tank electrical connector OK
- removed, cleaned, refitted and re-balanced the brass mixture screws (these were fairly shitty, so I had high hopes)
I also fitted the Power Commmander mixture gauge (analogue dial which connects to the PC module and displays air:fuel ratio), in the hope this would provide diagnostic information and went for another test-ride.
Still the same.
The PC gauge flicked between a rich 11%-ish (engine still cold of course) and 18% (maximum lean) when the surging happened.Searching this forum, I learned that a dodgy TPS may cause these symptoms, so I checked the voltage (pin 1 to pin 4 and pin 1 to frame earth). It was all over the place, between 0 and nearly 5 volts! Aha! Problem solved, I thought.
Nope.
Having disconnected the Motronic connector to get at the pins and stripped the tape off parts of the wiring loom to check the connectors and those supposedly trouble-prone bundled earth connectors, everything checked out fine and testing the resistance of the TPS at idle & full throttle, everything checked out fine. I did notice that pin 4 of the TPS doesn't go to earth as I would have guessed, but to pin 22 of the Motronic, along with the 'earthy' ends of the oil and air-temparuture sensors (circuit snip attached below).
So all I can conclude is that, during the failed start, where the engine didn't turn over, but the rev-counter indicated 2,000 rpm, the Motronic fried itself, resulting in the weird voltage readings on the TPS. I don't know why this happened, but I'm going to check the battery, earth and starter connections as the symptoms were like a flat battery, except it had started OK 10 minutes previously.
All comments and questions welcome - in the absence of other plausible explanations, I'm going to phone MotorWorks tomorrow to price up a replacement Motronic
