canadamaxxer
Pro
Posts: 1090
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posted May 29, 2004 05:09 PM
Gear position sensor info
I bought my bike used and since I have owned it, the FI light has been coming on at times. I checked the ECU and found that it was the gear position sensor code (I can't remember the #, but that's not important)stored in memory. The neutral light has been getting progressively more finicky and has stopped working entirely for hours at a time...only to start working again 5 minutes later. I changed the sensor and have noticed something unexpected: better fuel economy.
As some of you remember I have a 1270, with a Hindle pipe, etc, etc...I don't have high expectations of fuel economy. Since I installed the big bore the economy has been pretty bad (130-140 km until the low fuel indicator starts flashing --- around town, hard on the throttle [enjoying the new power]). I installed a new gear position sensor and that has gone up at least 60 km to a tank. It would appear that the sensor was not doing it's job in ways other than the nuetral light failures. I suppose this makes sense....the ECU is supposed to know what gear the bike is in...is this because the ECU has different base maps for each gear (as per some of the rumours out there)?
The problem is that we would never know what gear the ECU thought the transmission was in, without some kind of feedback. This make the idea of installing a gear position indicator attractive. I am talking about the public domain schematic, hard wired version, not the Acumen programmable unit. With the hard wired version, every shift would be slapping the rider in the face if it was not what was expected...this even includes any possible corrosion on the grounding button on the shift drum.
Speaking of the grounding button...when I had my sensor out, I pulled the button out, stretched the coil spring a bit, polished the tip of the button, and reinstalled everything. The system is working perfectly now.
Just an FYI.....
  
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beansbaxter
Needs a life
Posts: 5911
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posted May 29, 2004 08:55 PM
I wouldnt know what to tell ya. But by chance is the bike under warranty? Even though the motor has changed, it sounds electrical and would be covered.
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canadamaxxer
Pro
Posts: 1090
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posted May 29, 2004 10:36 PM
No Beans, it's a 2001 model....no warranty.
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Silver12rider
Parking Attendant
Posts: 3
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posted June 01, 2004 12:41 AM
Canadamaxxer,
Could you post a pic of the gear position sensor or tell me where it's located and what it looks like.
I'm also having trouble with mine. The netural light occasionally does not work and does not let me start the bike.
This only occurs when I park the bike in gear.
Thanks in advance for any info.
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canadamaxxer
Pro
Posts: 1090
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posted June 01, 2004 04:43 AM
The GPS (Gear Position Sensor) is located behind the front sprocket. Technically it is not a sensor, but is actually 7 switches in one assembly (one for each gear including neutral). The seven contacts are located radially around a 1" circle (approx) and contact a brass pin that is spring loaded and inserted (offset from centre) in the shift drum. The ground side of the circuit is completed through the transmission and through the black wire attached to one of the mounting tabs for the GPS. The way this sensor works is that the ECU is looking on all seven wires for a drop in voltage (the seven wires have 12v on them at all times). When it sees the drop on a specific wire , it knows that gear has been selected. The problem is that this switch requires a good ground path to work...which means the brass pin has to make good contact, and the ground path through the tranmission has to be solid as well...and the ground at the sensor has to be perfect. It is NOT a good system. I can think of at least two ways that this could be improved on. Personally I think wear is a huge factor....this sensor will wear out in time. Think about it...a spring loaded brass pin runs in an arc against seven contacts and the bakelite material insulating between them. Everything has to be perfect for this to work. The transmision should not be used as a ground path either. What engineer allows ANY current flow through a bearing race?
The sensor is not cheap ($100), so it might be worth it to try to clean the contacts and inspect for wear at that time. This is how I did mine: 1)put the bike on a rear stand. 2) loosen the chain and push the rear wheel all the way ahead. 3) remove the front sprocket cover. 4) Remove the front sprocket. 5) remove the screws holding the GPS into the engine case (they are very tight and are phillips head...use a hand impact driver to break the loctite free). 6) pop the sensor out (watch for the o ring to fall off the sensor, and the spring load pin to shoot outof the shift drum). Look for wear on the pin and on the sensor. I would polish the tip of the pin and stretch the pin spring a little bit. If you determine that you need a sensor, you will have to at least roll the engine down to get the 8 pin sensor harness connector routed between the engine and the frame...not a small job. The service manual says to remove the engine as the first step in the procedure...so you can guess how much fun it is to do. Also keep in mind that the sensor will fit in the engine case in two ways. Note the orientation before removal (unfortunately I have no pics of the sensor or the procedure).
Hope this helps
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BA
Pro
Posts: 1592
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posted June 01, 2004 07:21 PM
 Edited By: BA on 1 Jun 2004 20:21
FWIW, I'm pretty sure the engine doesn't have to come down for that but I could be mistaken.
Last year I replaced my shift forks and had some, ahem, assembly problems, but I had all those pieces in my hand by removing the clutch cover and the oil pan.
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canadamaxxer
Pro
Posts: 1090
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posted June 01, 2004 09:16 PM
The rectangular connector plug would not clear the gap between the frame and the engine. The removal of the sensor at the engine end is easy, and the connector is easily accessible if the tank is pivoted up, but the connector (at least mine anyways) will not go through the hole. I could move the harness cable back and forth in the gap between the engine and frame, but that's it.
BTW: I didn't lower the engine or remove it do mine...I cheated. I'm a flat rate mechanic....I can't help it.
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Silver12rider
Parking Attendant
Posts: 3
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posted June 02, 2004 01:40 AM
candamaxxer,
Thanks for the reply, this helps heaps.
I'll take a look at it this weekend.
Again thanks.
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canadamaxxer
Pro
Posts: 1090
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posted June 02, 2004 04:26 AM
No problem...let me know what you find
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