Joey, of Ballymoney, Northern Ireland, was the most successful rider ever at the TT, winning 26 TT races during his career.
He died on July 2, at the age of 48, following a crash in a road race in Estonia. Just weeks earlier he had secured a hat-trick of wins at the TT.
Anyone taking part in tonight's event, which starts from the TT Grandstand, is asked to give £10 to the Joey Dunlop Foundation, the charity set up in Joey's name, which has been converting a house at Braddan Bridge to provide holiday accommodation for disabled people.
All participants will receive a T-shirt.
The accommodation in Braddan was officially opened on Mad Sunday by Joey's widow Linda and 15-times TT winner John McGuinness who is the second most successful rider ever at the TT and a former team mate of Joey.
Chairman of the charity Kevin Quirk said tonight's lap on open roads will start at 7pm. Motorcyclists who have not booked in advance for the ride out but still wish to take part can turn up at the TT Grandstand at 6pm.
Kevin is delighted with the response the charity has had regarding the accommodation for disabled people. He said: "The number of enquiries we have had to stay there has been phenomenal. We cannot believe how many people have been in touch, it has far exceeded our expectations."