A forgotten tool left on the Factory Yamaha of Ben Spies contributed to his second MotoGP race crash of the season, during round three at Estoril on Sunday.

The tool is used to temporarily block the fuel overflow pipe on the grid, but was accidentally left in place for the race.

The tool's location adjacent to the front brake lever made it difficult for Spies to brake effectively, ultimately affecting his concentration which contributed in a crash with 15 of the 28 laps remaining.

"I am bitterly disappointed with today," said Spies, who dropped from fifth on the grid to tenth by the end of the second lap, where he remained. "After a lot of hard work by the crew this weekend we started the race with a very competitive set up and I was feeling good.

"When I noticed the tool hadn't been removed I tried to do it myself because it was right in there next to my brake lever. I managed to get it off but then this loose tube was flying around which was pretty scary.

"It really messed with my concentration as I was worried about taking out another rider in one of the corners and then I crashed.

"After the DNF at Jerez this was really frustrating as it was completely out of my control, nothing to it now but to move on and come back strong for Le Mans," concluded the American, who made contact with countryman Nicky Hayden during the race.

The incident marked a further dose of Estoril bad luck for Spies, who didn't even start last October's race after falling on the way to the grid.

"Ben has again been unlucky at Estoril," said team director Massimo Meregalli. "It is unfortunate that sometimes these human errors occur in racing at all levels. Fortunately he was uninjured and was able to avoid involving any other riders in the incident."

Spies' team-mate Jorge Lorenzo finished second on Sunday.