He is to ride for Two Two Motorsports, replacing injured Australian superstar Chad Reed on the bike. Reed is also Two Two Motorsports' team owner/rider and he is also a multiple US supercross and motocross champion.
"After surgery and the initial realisation that I would be sidelined from competition for some time, I needed to consider the team's ongoing development and if there was a rider that could step in and be competitive in the role," said Reed.
"Ben has had success at the highest level of motocross. He knows what it takes to win, and work in a close, team environment. I believe he can be competitive and can be a contender in the outdoors championship."
Carlton Dry Honda Thor Racing Team owner Yarrive Konsky and general manager of Honda Motorcycles Australia, Tony Hinton, were approached by Reed to discuss the possibility of Townley's release from the Australian factory team.
With Townley's career prospects in mind, both parties agreed to support the move.
"I have just come off a rebuilding phase and everything is heading in the right direction," said Townley.
"I have been working on mental strength and on riding technique during the New Zealand Motocross Championships.
"I have been able to elevate my riding to a new level and I believe I have really showed - pretty much winning everything I've entered here (in New Zealand) - that I am in the best form of my career at the moment.
"It was a tough decision to leave the Carlton Dry Thor Honda Team because I have been very committed to this team in Australia and I wish them all the best. It was a delicate process to handle but they've been great and given me their blessings."
The man who managed the Bel Ray Honda race team during the nationals in New Zealand, Auckland's Peter Finlay, said it was a "real pleasure to have Ben race here".
"We knew we wouldn't have him for long in this part of the world. He's an international star and we were just fortunate to have him to race here this summer," said Finlay.
Townley will still contest the opening round of the Australian nationals this weekend before he begins pre-season testing in the US.
The 12-round US series kicks off at Hangtown, in Sacramento, on May 19.