The German importer for Benelli in the 1980s was a gentleman named Manfred Demharter. Manfred didn’t just sell bikes – he liked to race them, too! Because of that, he often built (or sourced) custom frames to stuff Benelli six-cylinder engines into.
Per the seller, this bike weighs just 357 pounds – compare that to the stock bike at 562 pounds! “Not a great deal is known about the actual frame designer/fabricator engaged by Demarter; he did use an Elby-moto frame but being German, the frame on this example has many design features found on those from Rau Tuning. In the late 70’s early 80’s Manfred Rau was a brilliant young designer making quite an impression in the German Superbike Championship with his Egli-styled back-bone frames.”
The stock motor produced 71 horsepower – this one presumably makes a little bit more. That kind of power in a 357 pound bike is impressive even today (a Husky 701 SM makes 74 hp and weighs about 320 lbs), back in the 70s it must have been a revelation.
Find this Sei for sale in Coffs Harbour, Australia for $26,765 USD here on Raider Moto.