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Discussion Starter · #1 · (Edited)
The dealer fit Datatool Veto on my 1999 R1 finally gave up last week. Whilst the AA man was trying to bypass it he applied 12v to some of the cables and I think this blew a diode in the safety relay unit. The symptom being that the neutral light turned on when the sidestand was raised! The neutral detection switch appeared to be non functional. I was able to start the bike with the clutch in and the sidestand up however. It would not start with the sidestand down even when in neutral.

The relay unit uses diodes to combine the signals from the neutral switch and sidestand switch to control the signal to the relay that enables the starter button to crank the engine. Having worked out the wiring I concluded that the only way I'd be seeing this symptom was because of a blown diode in the relay unit.

This is the unit on the wiring diagram - note the connector shape and pins. It is located on the rear left-hand side of the seat compartment. On the diagram it shows the wiring colour on the cabling connector, not the unit itself - where the connections are reversed.

Rectangle Font Parallel Slope Diagram

The wiring colours are decoded using this table:

Font Rectangle Circle Number Screenshot

From online resources it looked like I could order a replacement part with the same main part number: 18950 - I ordered one for an R6 ending in -40. However, when it arrived the connector was different and having opened it up it clearly has more functionality than the 1999 unit, as well as more compact relays. I figured it would be useful for spare parts, and opening it up enabled me to determine the best way to open my own unit.

Brown Rectangle Wood Carton Packaging and labeling

If you cut the unit open with a hacksaw by gently cutting through the shell in these places (all the way round back from the connector and under the printed top) it should come apart with a little bit of prying. Note that the relay units are glued to the housing, but it is the kind of glue that 'pulls' apart when gentle, constant pressure is applied.

Make sure you get the cuts at the same distance from the label side - this places them in line with the PCB. Take it carefully and you should be fine.

Brown Food Wood Rectangle Cuisine

This is the 1999 R1 connector layout:

Brown Circuit component Rectangle Electronic component Electronic device

Inside the relay unit there are two relays (black boxes with manufacturer Omron), four diodes (black cylinders with a white bar around for orientation which is important) and two resistors (brown cylinders).

Circuit component Electronic component Hardware programmer Passive circuit component Electronic engineering

The diode closest to the housing (bottom of picture above) looked like it might have sustained trauma, and looking at the wiring these two diodes combine the neutral switch and sidestand switch inputs.

Brown Amber Rectangle Material property Food

The underside of the 1999 R1 unit is shown above. The dodgy diode is top-left in the photo.

The R6 unit contains more of the same diodes so I carefully desoldered one and replaced the one in the R1 unit. The solder wasn't particularly great on mine to lift - normally desoldering tape helps draw the solder off the PCB but this is probably lead-free solder which is much harder to work. In the end I heated the ends of the diode leads with the tip of the iron and then manipulated the ends through the PCB. The risk is you'll lift the PCB track around the lead, but you can always scratch off the green solder resist on the track with a stanley knife and solder to that if the pad is damaged.

Having replaced the bottom diode I found that the neutral light switch no longer turned on when the sidestand was lifted. I tested the extracted diode and it was dead (a multimeter continuity setting can be used to check diodes - they should be open circuit with the leads one way round, with some sort of measured resistance in the other). I decided to replace the other diode, but that didn't make any difference.

Then having checked the sky blue lead into the unit I found the neutral switch didn't ground when in neutral - no difference no matter what gear was selected. I then checked the screw head on the sensor itself (it can be seen on the gear housing infront of the main spring) with the same result. There is a connector to the sensor under the fuel tank on the right hand side - the sky blue lead again. So either the sensor has been broken at the same time, or just failed coincidentally. I've ordered a new one from Yambits : Yambits - Yamaha Parts and will update this post when everything is now working fine.

Hopefully this will help someone although it is probably a rare failure mode. I can post my determination of the wiring into the imoblizer connectors if that helps someone determine the correct bypasses on a failed unit.

Regards, Mark.
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