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Discussion Starter #1
So I decided to upgrade my 1999 ST4 with the Yamaha starter relay sold by ca-cycleworks. When I "unwrapped" the old harness connector found something which looked like a resistor running between the power and ground sides of the OEM wire harness connector for the starter relay (see photo). Anyone know if this is normal? Did a previous owner maybe hack it together?



Wayne Beaver
99 Duc ST4
 

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Its a diode, helps protect the driver when the solenoid turns off and generates a kick-back voltage. Good idea with any high-current coil.

pg
DD
 

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Discussion Starter #3
So, sounds like something I should "wire back in" when re-assembling the harness side for the new relay connector then, right?
 

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Paul is right. Diode that soaks up the CEMF spike when the coil is de-energized. Thanks for the great pic!
If you do replace the connector with a unique one, just make sure that the new diode goes in THE SAME WAY as the old one. Rule of thumb: make sure it's reverse biased for when the power is applied to the solenoid. If ya do it backwards, it'll fry instantly when you push the start button, and you'll be doing it right the 2nd time...
 

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Discussion Starter #5
Thanks, Stick, I'll make sure to mark the old diode, and/or disconnect/re-connect one-side-at-a-time (slowly).
 

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It is marked (as are most diodes). The cathode is marked with a band of silver/white paint. That goes to the positive wire (blue/red in this case).

Cheers

pg
DD

Thanks, Stick, I'll make sure to mark the old diode, and/or disconnect/re-connect one-side-at-a-time (slowly).
 

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Discussion Starter #7
OK, so one final question.My positive wire from the harness is blue/red. Ground wire form the harness is black. The Yamaha relay has one red/white wire and on blue/white wire. Should I connect the harness's blue/red wire to the relay's red/white wire?
 

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Its probably just a coil, so is insensitive to polarity. Put an ohmmeter across the contacts both directions; if the resistance is the same in both directions, then polarity doesn't matter.

pg
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Both wires pulled out of connector on new starter relay

I just replaced my relay with the PN 21-2988 Yamaha one from CA-cycleworks bought in February of this year.

Heads up to all, I found that both wire crimps in the relay harness were bad and both wires pulled right out. Luckily I found this out after I had to remote mount the diode since one of the leads was too short to recrimp it into the new connector.

Needless to say, its not easy getting the terminals out and you have to be extremely careful when recrimping them. I soldered the crimp then had to cut the harness connector and make a splice to add in the diode.

A real pain but now that everything is together and soldered, I can relax when on the road.

The other option I considered was to buy another pair of connectors.

Bob
 
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