Manxman clarification
Referring to your correspondence with Roy Downing (TCM, YWA January 2022, page 84) regarding the Beasley Manxman Mystery, I can further clarify Excelsior’s Lightweight and Junior Manxman (twovalve) race engine dimensions.
The first lightweight (250cc)
Manxman engines manufactured in 1935/6 had 63x70mm bore and stroke dimensions to give 246.29cc. Later engines manufactured 1937-9 had revised bore and stroke dimensions of 67x70.65mm, giving 249.12cc. Junior (350) models were manufactured as 75x79mm bore and stroke, 1935-9, to give 349.10cc. Doug Beasley used ‘squarer configuration’ for his Manxman lightweight engines of 68x68mm bore and stroke, giving 247.98cc.
Stuart Jukes, email, IoM.
Thank you, Stuart, for confirming 250/350cc factory and Doug Beasley’s Manxman dimensions. And I’m sure Stuart won’t mind this column mentioning his 249.12cc Excelsior Manxman GR11 racer was delightfully featured by Dennis Frost in TCM, April 1997, pages 4-7. The accompanying specification panel for the feature informs the 295lbs machine developed 22.5bhp and 7350rpm, giving a top speed of approximately 90mph. Little wonder Doug Beasley and others used Manxman power for their 250cc special racers.