Primary Chain Tensioners

Tensioning devices for the primary chains: transmission tensioner

Since the engine was firmly bolted into the frame, Harley-Davidson came up with a way to bring the primary chain to the correct tension: the sliding gearbox. The stud nuts under the gearbox were loosened, the gearbox was brought into the correct position with a tensioning screw and the stud nuts were tightened again. Easy, simple, ingenious. If only the tension of the rear wheel chain hadn't changed every time. So both chains always had to be readjusted. But well, there's always a fly in the ointment... In any case, that's why there are gear tensioners for tensioning the primary chain.

Tensioning devices for primary chains: Tensioning shoes in the primary box

Of course, there is no need to retighten the rear chain if the primary cover is solid and prevents the gearbox from shifting. However, a tensioning shoe has been integrated into the aluminum primary to ensure that an insufficiently tensioned primary drive chain does not grind inside the housing. Accessory tensioners are available with fixed tension or spring-support for Sportster (original!) and Big Twins from DynaMite and Hayden.