I sold a restaurant the balloon payment was 2013 he didn't have it so we moved date to 2015 due in march no money can i lock him

First step is to review the written documents to determine what the remedies are for breach. If you are not sure, talk to a business lawyer, especially before trying a lock out. Be well.

No, you are not legally permitted to lock anybody out without court process.

Dear Clayton Property Owner: Unless the contract provided the remedy of repossession of the restaurant in event of a default in paying off the sale price, you may have nothing more than an action for specific performance or breach of contract or the right to enter a money judgment (your contract should provide all the information you need). So you may have sold the restaurant cheap since the purchaser cannot pay you, and now may not have assets to pay a judgment.

An attorney would need to review the terms of your sale agreement and documentation. If the sale was properly secured you may have the right to repossess the business. Take all if your sales agreements. And documentation to an attorney for review.