Primary Drives


The Harley Davidson primary drive (by which we mean the drive connection between the engine and the gearbox) is extremely robust in all forms, rarely requiring attention other than routine maintenance and oil changes. However when a bike has high mileage or previous owner abuse, new parts can be needed to return the package back to proper operation.
Pictured below is a recent client disaster. The Evolution FXR bike was brought to us with "a funny noise". When we stripped the primary drive down, the damage pictured was the result of a Japanese only workshop performing a cheap service, the bill to rectify this work was not cheap!



The clutch on the more modern Big Twin models (1984 onwards) is of a diaphragm type and generally very good, requiring little in the way of attention on normally ridden street bikes. However if you go proper racing or have a propensity for "fast" traffic light starts, the clutch wont last very long. The replacement of a heavy diaphragm spring is a good idea, but does result in a heavier than standard clutch action. However various modifications are available to relive this heavy action. The later Big Twin models (1985 onwards) require the whole primary side to be disassembled when attention to the final drive belt or the pulley is required.



Shovelhead (1966-1984) and earlier clutches are all relatively similar in design, although they have 3 and 5 spring design, when set up well, can last a life-time. In our experience the majority of problems are either related to bad workmanship by previous owners or simply bad adjustment and occasionally annoying little things like being overfilled with oil.



The clutch and primary drive is invariably part of any engine work. As they have to be dismantled to remove the engine, at this stage it is of paramount importance to check, clean, inspect and replace any worn parts.

If you have any issues with the primary drive and clutch, Blueprint Engineering will be able to assist, allowing you to get back on the road as quickly as possible.

Call Joe on 01902 338265 9am to 6pm, who will be happy to help.


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