Judd, who was not wearing a helmet, suffered head trauma and was flown to Missoula, Mont., on Thursday afternoon. He was diagnosed as brain-dead and was being kept on a ventilator so his organs could be donated, authorities said.
The Utah AFL-CIO said Judd was in Montana participating in the International Association of Fire Fighters motorcycle rally in Butte. Judd also is vice chairman of the Utah Democratic Party.
"He is one of the best labor leaders I've come across," said Dale Cox, vice president of the AFL-CIO in Utah, an umbrella organization for many of the state's unions. "He was in a motorcycle accident and was in critical condition, and we're just waiting for word."
Judd served as vice president of the AFL-CIO and became president in 2007 when then-president Ed Mayne, who also was a state senator, died of cancer.
"Oh, golly, it's hard," said Karen Mayne, Ed Mayne's widow, who also now serves in the Utah Senate. "Whatever happens, it's a strong movement, and we'll move on."
Wayne Holland, an international staff representative for the United Steelworkers in Utah and portions of nearby states, said Judd loved motorcycles and participating in charity rides with union members.
"It's just a tragedy for all of us," he said.
Judd became involved in the labor movement in Las Vegas in the 1970s when he joined the Teamsters. He moved to Utah in 1977 and went to work for the Ogden City Fire Department, where he became a member of the Professional Fire Fighters of Utah Local 1654. He was elected local vice president in 1978 and became president the next year.
"I've known Jim for 35 years," said Randy Atkinson, president of the 9th District of the International Association of Fire Fighters. "This is just terrible news."
Judd was elected president of the Professional Fire Fighters of Utah in 1985.
Jack Tidrow, a Salt Lake City firefighter, succeeded Judd as president of the state group in April 2011.
"We're just praying right now. That's all we can do at this moment," said Tidrow. "Our thoughts are with him and his wife, Jill, and the entire family, his actual family and his labor family."
"Jim was a close personal friend," said Jim Dabakis, chairman of the Utah Democratic Party. "He lit up every room he walked into, his smile was magic, his mind like a steel trap and his dedication to justice and service were an example for us all. I will miss my closest and dearest councilor and his loss to our party is incalculable."
Anna Thompson, Utah Democrats communication director, said in a news release that Judd's passion and vast experience will be missed.
"Jim had an immeasurable impact on our state, and his loss will be felt by all who have met him," she said.