Shakey225 Posted January 10, 2021 Posted January 10, 2021 Bike is a recently imported (from NL) GSX 750 ES from 1988. The Problem: When on the centre stand the bike can be started, put into first gear and the clutch let out - all is well. As soon as the bike is on its wheels with the centre stand up I can start the bike in neutral but as soon as I engage first gear the bike stalls and the side stand warning light comes on. The side stand switch has been removed in the past and the wires cut and sealed. If I remove the wiring from the plug connector, the above situation occurs. If I connect together the two wires that run to the s/stand switch then the same occurs but with the s/stand warning light illuminated continuously. Looking at the wiring diagram (supplied by the previous owner) I can see there is the s/stand warning light switch, a diode in the dashboard wiring between the s/s warning light and the oil pressure warning light, and there is a starter lockout switch between the starter relay and the starter button. I have traced the G/Y wire from the relay, under the tank (which I removed) all the way to the handlebar switch. No lockout switch... Does anyone know where this lockout switch is located? I am assuming there must be a wiring issue that is affected when the rear shock is compressed but need to locate everything in order to check. I have checked all earth mounting points that I can find and have a replacement s/stand switch on order to see if returning to standard solves the issue. Any thoughts welcome. Quote
jensvonbustenskjold Posted January 10, 2021 Posted January 10, 2021 Hi You might wanna share your diagram. There's many versions. Helpful looking at the same sheet. Quote
Shakey225 Posted January 10, 2021 Author Posted January 10, 2021 35 minutes ago, jensvonbustenskjold said: Hi You might wanna share your diagram. There's many versions. Helpful looking at the same sheet. Of course... Quote
TonyGee Posted January 10, 2021 Posted January 10, 2021 cant read the wiring diagram as it goes blurry when i zoom in, but it does sound like theirs a switch on the centre stand !!!!! never seen one before but worth a look i suppose just in case Quote
Isleoman Posted January 10, 2021 Posted January 10, 2021 Great presentation of the problem. It seems like your electrical circuit thinks the side stand is down when it's sitting on it's wheels and appropriately cuts the motor when it's put into first. I can't imagine why an owner would want to defeat this critical safety feature. My 1974 Z1 didn't have that feature and I went down at 35mph on the first left and corner I came to when I forgot to put the side stand up and got under way. The fact that it doesn't think the same thing when it's on the center stand suggests the wires that have been cut to the side stand warning switch are either closing or opening (depending on how the switch works) from the weight of the bike pressing on the wires (creating short). That's all just a guess. I'd find a switch and put wiring back to to OEM. Can you unwrap the cut wire from the side stand safety switch and touch them together while doing the same procedures you outlined? You should see the bike shut off while on center stand (correct response) if I'm right. Shouldn't make any difference on it's wheels. Again just a guess. Try it with and without those wires connected in each scenario. 1 Quote
jensvonbustenskjold Posted January 11, 2021 Posted January 11, 2021 (edited) It seems that the previous owner has done something wrong. If the side stand light is illuminated by the gearing into 1st gear, I would trace that circuit. According the schematics, the side stand switch is an NO circuit. It's the only switch that should illuminate the lamp. Start at that lamp and following backwards. Why is it connected together with the neutral switch? That's the real question. Disconnect the neutral switch and see what's happening? @Shakey225 EDIT: The schematics you have uploaded does not contain a side stand relay, as far I can see. Got me thinking, since you mentioned it. Have a look at this manual, page 304. The engine kill-switch and the side stand are pulling the stand relay. So, if the side stand light is illuminated, then this relay is pulled. Are you sure the relay is removed? As you can see you have something called "side stand diode". The diodes acting a logical "or" block. Both the side stand switch, and the neutral switch are connected to ground/negative, and the other end is connected to the "side stand relay". Both the neutral and side stand switch can kill the engine. You have to find out what the previous owner did by reverse engineering, tracing wires. Edited January 11, 2021 by jensvonbustenskjold 3 Quote
Shakey225 Posted January 11, 2021 Author Posted January 11, 2021 13 hours ago, jensvonbustenskjold said: It seems that the previous owner has done something wrong. If the side stand light is illuminated by the gearing into 1st gear, I would trace that circuit. According the schematics, the side stand switch is an NO circuit. It's the only switch that should illuminate the lamp. Start at that lamp and following backwards. Why is it connected together with the neutral switch? That's the real question. Disconnect the neutral switch and see what's happening? @Shakey225 EDIT: The schematics you have uploaded does not contain a side stand relay, as far I can see. Got me thinking, since you mentioned it. Have a look at this manual, page 304. The engine kill-switch and the side stand are pulling the stand relay. So, if the side stand light is illuminated, then this relay is pulled. Are you sure the relay is removed? As you can see you have something called "side stand diode". The diodes acting a logical "or" block. Both the side stand switch, and the neutral switch are connected to ground/negative, and the other end is connected to the "side stand relay". Both the neutral and side stand switch can kill the engine. You have to find out what the previous owner did by reverse engineering, tracing wires. Thanks for your thoughts and the link. It does indeed seem like there is a relay or diode somewhere in the mix causing issues but I'm b***ered if I can find one anywhere. I will try tracing the s/stand light back as you suggest. Thanks again jensvonbustenskjold 1 Quote
Isleoman Posted January 11, 2021 Posted January 11, 2021 The fishe for the 88 GSXr shows the side stand relay under the left side cover. Not the same bike but under the side covers would be the logical place for it. https://www.babbittsonline.com/oemparts/a/suz/50d3c30af870021958f2748b/wiring-harness-model-j-k Couldn't find your model 2 Quote
jensvonbustenskjold Posted January 12, 2021 Posted January 12, 2021 Found this. If you're not up to fault searching, you might wanna rewire the bike. Rupe has rewired his bike, and left a pretty diagram. https://rupesrewires.com/grahams-cafe-racer/#prettyPhoto 1 Quote
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