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Monster 620
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Discussion Starter · #1 ·
I have an old 2006 Monster 620. I've ridden about 10 000 km (~6200 mi) but on my last ride, my battery died while the engine was running.

I checked my regulator first, when I came home, and measured around 5-6v on the output (!). I ordered a new regulator and I'm waiting for it to arrive, but then I thought to also check the alternator too.

One of the pins on the alternator connector (to the regulator) was burnt and melted into the connector housing. I pulled the pins out and measured the phase voltages at around 1k engine rpm. Assume that the melted pin's wire was phase 1.
Phase 1-Phase 2: 16v
Phase 1-Phase 3: 7v
Phase 2-Phase 3: 14v.

I also measured the resistance: 1-2 and 2-3 were around 0.23 ohms, but phase 1-3 was around 0.17 ohms.

I also probed it with an oscilloscope:
Phase 1-2:
226804


Phase1-3:
226805


It looks to me like the coil on phase 1-3 is shorted somewhere inside the alternator, or something like that. Should I start looking for a new alt? Is it possible that my bike will run with the new regulator with an alternator like this (temporarily)? Does it make sense to rewind the alternator, instead of getting a new one? Any experience with this is appreciated.
 

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Interesting to see this on an oscilloscope. I haven’t gotten to ply with one in years. It sounds like one phase of you stator/alternator is fried. I’ve heard of stators taking out regulators, so I wouldn’t recommend installing the new regulator without the new stator. I haven’t experienced it first hand, but I would hate to see you have to replace a second regulator. I’m not sure where you are from, but in the US Rick’s Motorsport Electrics is a solid source of regulators and stators. I’ve used their stuff on several of my motorcycles and they do have international shipping, if there’s nothing closer to you. Make sure to get whatever gaskets you might need to finish the job too.
 

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Discussion Starter · #3 ·
Okay. I pulled out the stator. As I expected, one of the phases looks toasty. Lots of oil cooked and caked up on it.

226807


Furthermore, some absolute barbarian installed the left case without a gasket. I am in awe. I guess my bike will be out of office for a while.

I haven't mentioned it, but I live in Slovakia. I'll see into that company in case I don't find anything here, but I think I will.
 

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Hoped you can get back on the road soon. That definitely looks fried. I’ve had a few bikes with fried stators and they all looked like that when they came out.
 
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