According to the workshop manual which can be found in the File Vault section of the forum, page 1-10 shows the ratio to be 2.688 (43/16) - which means 16 teeth on the front and 43 teeth on the rear.
Be careful if you are considering changing the sprockets for any other size, as this will affect your speedo reading and will also affect acceleration, if you put a smaller sprocket on the front you will accelerate better, but top speed will be lower. If you change sprockets don't forget you also need to replace the chain........