Thousands of cyclists took to the roads this weekend for the 33rd annual Pan-Massachusetts Challenge charity bicycle ride. The fundraiser for the Dana-Farber Cancer Institute’s Jimmy Fund kicked off Friday with opening ceremonies in Sturbridge and ends Sunday in Provincetown. Nearly 2,700 riders left Sturbridge in the pre-dawn hours Saturday for the main event, a two-day, 190-mile ride. Earlier today, another 2,100 riders left from Wellesley for other routes of varying lengths. This year’s Pan Mass Challenge cyclists will ride with the goal of raising $36 million for Dana-Farber.