ORIGINAL: av8tor1977
Yes, I can verify that if the Avgas evaporates, the rubber components will dry out very quickly. I have a race boat that I use Avgas in, and when it sits long enough for the fuel to evaporate out of the carbs, the "O" rings on the inlet needles in the Holley carbs dry out and shrink. Then when I go to start it, it floods like crazy and I have to remove and replace all four needle valve "O" rings. The accelerator pump diaphragms take a beating too. Though as a matter of fact, I just had this very thing happen on my Blazer as well a couple of weeks ago, and it only runs on premium pump fuel.
AV8TOR
My DLE55 was run exclusively on avgas until mid 2011. Since then it's on the shelf, completely bone dry. I intend to run the 55 again this year so I'll get some first hand info oh how the walbro behaves. On your experience it's worth the time to take the walbro apart and feel the rubber. I'll post the findings, good or bad...