What is the Statute of Limitations in California for collection of unpaid HOA dues?

4 years I believe as it is a written agreement/contract. BW

Correct, statute of limitation in California for breach of written contract is 4 years. California Code of Civil Procedure Section 337 This means that the creditor has 4 years from date of breach (unless SOL is tolled) to sue. If sued within the 4 years, a judgment in California is good for a period of 10 years, and can be renewed infinite number of times as long as it is renewed before a 10 year period expires.

The dues may become a lien that runs with the land. So while you own the land there is likely no statute of limitations. After you no longer own the land then I would assume that it would be a 4 year statute of limitation on written contract.