Former Wigan rugby league player Howarth previously headed up the Tena for Men squad in 2008 but most recently had been racing in the Pirelli National Superstock 1000 Championship.
Cheshire's Mainwaring enjoyed podium finishes in last year’s Superstock class while Midlander Quigley competed in 10 rounds for GBmoto Honda last season with a best result of 12th.
Howarth said: “The decision to run the team stemmed from the end of last season when I raced in Superstock. I want to have a team that is enthusiastic and I really want to do the job properly.
"I have really big personal goals for the team and high expectations of both of the riders. I want to beat what the team we had in 2008 achieved as a start and then who knows what we can do as this is a long-term project.
"I have so much enthusiasm and that is what you need to be successful in racing. The combination of me wanting this team to be a success, plus a pair of dedicated riders whose ultimate passion is racing, should be an exciting prospect.”