In my eight years of WR400/450 ownership, I finally experienced a component failure. After blowing three bulbs in a row on my 450 and THEN () deciding to investigate/troubleshoot the issue, I narrowed it down to a blown Regulator/Rectifier. The output at the bulbs was between 20-25 VAC depending on rpm, while strangely enough the output across the battery never exceeded ~14 VDC. The battery never discharged and the e-start always worked, so the DC side of the R/R seemed to be working fine. While troubleshooting, I went through the process of disconnecting/connecting/cleaning all connectors with no success, so I finally borrowed a R/R from a friend's 450, and problem solved! The output at the headlight was now 9-12 VAC depending on rpm. A couple of minutes on ebay and $45 later, I'm back in business with a used 2007 WR250F Regulator/Rectifier.