I keep blowing regulator rectifiers on my virago 250cc

Is there a good battery installed? A battery functions as a voltage regulator. Without a battery, there is no voltage regulation and you can blow the light bulbs easily.

That happened to me last year on my virago 1100. Battery would fully charge, but not hold once in the bike. It was a brand new battery from GP Bikes. I took it back to the store and they checked the charge with their machine, which is better than mine. The battery was a lemon. They replaced it and the new one worked perfectly. But what a pain for a few weeks to figure out it was the battery and not the bike.

The bike probably has a faulty charging system. Need to check regulator/rectifier for proper operation as well as the stator's output voltage on all 3 phases. They usually blow out the regulator though.

I HAVE YZF R6 2003, WHEN I START THE ENGINE AFTER ALMOST 5 MINUTE RECTIFIER REGULATOR OVER HEATING AND DAMAGE CONECTION

I have a 94 virago that had that problem last year. First, is your starter switch releasing all the way out? Mine was sticking. Also the regulator-rectifier needed replacing, as it was no longer damping the current, which leads to surges, especially when revved. If you have a manual it will tell you how to check the current running through the bike. Replacing the regulator is cheap and easy even for me with my limited bike knowledge! Hope this helps. Charlie.

Sounds like you have a short somewhere. Check that all your connectors and wires are in good condition with no insulation worn through. Also check that all your connections are tight.

There is a good manual with free tech support for your Virago 535 at: http://www.cyclepedia.com/yamaha-virago-xv535-online-service-manual/