Gents, A Marquart MA-5 Charger I've been looking at buying had the upper wing tanks rupture due to the installation of motorcycle fuel caps that let air in the tank, but wouldn't let it out (like on my HD, the fuel has an overflow expansion drain line) Thus, after filling the tanks and letting the aircraft sit in the sun, the upper tanks ruptured due to expansion of the fuel inside, letting 10 gallons of AVGAS run back through the upper wing structure and out the trailing edge of the wing, all near the center section, maybe 3 to 4 feet outboard from center (and mostly to the right side, it seems.) Don't know how long it took for the gas to drain, how long the wood was soaked by AVGAS. The owner couldn't fully answer if any attacking of the rear spar varnish, wood, and other internal wing parts had happened. Further, it seems no inspection has been done to look and see. Access would certainly be difficult, I agreed. But still... I think this happed a couple of years ago, maybe less, but the airplane has been flown regularly since this happened. Anyway, I'm wondering if AVGAS attacks wing spar varnish, and/or the wood itself. Are there structural concerns here that would make a purchase unwise? Thanks in advance.