3/23/13

XS650 project

There are a few ways to increase the reliability and performance of the XS650 charging system. There are complete permanent magnet alternator(PMA) kits, or plug and play solid state regulator/rectifiers. On my '75 I'm doing the Pamcopete Chrysler regulator and Radio Shack rectifier swap. I like this in that it uses proven, yet very low cost parts that are readily available.

The old mechanical regulator and the new Chrysler regulator, part #VR733 from Autozone. I also bought a connector for it, but you can just use bullet terminals.
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The old rectifier, and two 276-1185 full-wave bridge rectifiers from Radio Shack.
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The Chrysler regulator needs the alternator to be modified to work like '80-'84 models by isolating the inner brush. This is done by replacing three steel screws with nylon. The nylon screw were the only thing I didn't buy locally. I bought a 10 pack for under $4 shipped from ebay seller AMS Bugbolts in the UK.
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The M4 12mm nylon screws in place.
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This is the alternator connection on the main harness. The black wire was ground, but needs to go to a switched 12V power source (brown wires) with an inline fuse.
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The new regulator connector soldered in place. Green to green, and blue to brown. The Chrysler regulator grounds through the case, so the black wire gets a ring terminal.
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There are many ways to mount the regulator. I used one existing mount (bottom front), and drilled two holes in the battery box for the rest.
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I had some scrap 1/8" x 2" aluminum flat stock and cut a 3.5" piece to make the heat sink/mount for the rectifiers. Heat sink compound is used for this.
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The original connector cleaned up nicely and was in good shape, so I reused it.
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Done and mounted. The rectifier mounts in the stock location under the battery box.
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This is with the side cover on to check clearance. The wires are close, so I'll probably use some stick-on foam to make sure they don't ever rub.
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A few more electrical parts, the bigger one on the left is the 'safety relay', which I'm going to keep. It cuts power to the starter once the engine is running. I don't know why they thought it was needed, but I guess it doesn't hurt anything. The gray box in the middle is the 'light checker' and the small cylinder on the right is a diode for the brake lining switch. Both of those won't be used. I went through the harness and removed the wires for them also.
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