Possibly.  Massachusetts General Laws Chapter 90, Section 7N (commonly known as the “Lemon Aid Law”) allows a buyer to void a contract and return the vehicle if it fails to pass the safety or emissions inspection within 7 days of the sale AND the estimated cost of repair exceeds 10% of the purchase price.
 
The law applies to dealers and private parties and covers cars and motorcycles purchased for family or private use. Note that the inspection must be performed within 7 days of the purchase, and only those repairs that are required for the vehicle to pass the safety or emissions inspection can be included in the calculation of the 10% threshold.
 
If you did not get the car inspected in time, you can look into the MA Used Car Warranty Law (Massachusetts General Law Chapter 90, Section 7N1/4), which states in part:
 
(8) A private seller shall clearly disclose to any prospective buyer, before the sale is completed, all defects the seller knows of which impair the used motor vehicle’s safety or substantially impair its use. Failure to so disclose known defects shall entitle the buyer, within thirty days after the sale, to rescind the sale and be entitled to return of all monies paid to the seller less a reasonable amount for use as defined in clause (iv) of paragraph (A) subsection (3). In any subsequent action by a buyer under this section, if the court finds that the settlement offer was unreasonable in light of the circumstances or that the private seller has otherwise failed to comply with the requirements of this subsection, in addition to damages, it shall award the buyer reasonable attorneys’ fees and costs; if the court finds that the buyer’s action was frivolous or not in good faith, it shall award the seller reasonable attorneys’ fees and costs. It shall be an affirmative defense in any such action that an alleged defect does not impair the vehicle’s safety, or substantially impair its use, or that it is the result of the buyer’s negligence, abuse, damage caused by accident, vandalism or attempt to modify the vehicle.

Because of the amount of money involved, you will likely be pursing this without the help of an attorney.  If I were you, I would do some research and then send a demand letter to the seller.  (A good place to start your research is the MA Office of Consumer Affairs: http://www.mass.gov/?pageID=ocahomepage&L=1&L0=Home&sid=Eoca).  If he refuses to refund the money and you have some free time on your hands, you can sue him in small claims court.   Good luck.