I found that my 650 had a miss at high rpms. It could be a number of things, but since the ignition system was essentially brand new and the carbs were just aggressively cleaned, jetted, and synchronized, I decided to start my troubleshooting with the charging system. I have a boyer ignition system and I understand it is more prone to issues with anything less than perfect voltage.
First I checked the battery voltage with no lights on and the engine running at 2k rpm. The manual says 14.2 - 14.8 is the acceptable range. I got 14.15 volts. Not too far off but not in range.
Next I checked my rotor. According the manual it should have 5.7 ohms between the rings. Less than 5 would be a failure. I got a reading of 4.6 ohms. Doh, 1 part failed.
Next I checked for a short between the each ring and the center nut. Thankfully neither ring is shorting out. That passed.
Next I checked the the wires out of the stator for resistance. The goal was to have 0.46 ohms of resistance between any two of the three white wires. My readings were infinite, 0.7 ohms, and 2.9 ohms. Every one failed. Additionally, I found burn marks at the wire terminal. As far as I can remember this is the stator off my parts engine, rather than the one that was in my original engine when the pick up coils melted.
Clearly there are some issues with the charging system. Whether or not they are leading to my high rpm miss has yet to be determined. Rather than replacing all the individual components with OEM parts, I am looking at a permanent magnet swap. If I am replacing lots of the parts anyways, I might as well. From what I hear, its lighter, provides more reliable power, and is maintenance free. Only time will tell.
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| funny, i got a fairly stead 4.6 ohms at several different points, except when taking the photo |