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Replacing Springs on the BMW R65 Advance Mechanism

The R65 has electronic ignition, but with mechanical advance controlled with centrifugal weights. A fast engine idle after a highway run can be a symptom of the return springs being stretched or tired.

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The first step is to disconnect the battery and then remove the front engine cover. The bean-can can then be removed by undoing the two holding screws and easing it from the housing.

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The spring on the nose of the unit can be unwound and.......

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......then the holding pin can be removed by clamping the tangs of the drive dog securely and drifting the pin with a punch.

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Behind the drive dog there should be a fibre washer, sandwiched between two steel washers.

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On the other end of the unit the cover can be removed by undoing the two screws and easing it free.

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Next the bearing plate can be removed by undoing the next two screws.

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The large securing ring can be extracted using circlip pliers or similar.

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To remove the inner workings, the cable gland needs to slide in the housing. To enable this, the plastic rivet should be pulled clear.

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With the other three housing screws released, the inner mechanism can then be extracted out the back of the can.

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With the mechanics exposed, the springs can be replaced using tweezers or needle-nosed pliers.

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This photo shows the old, stretched spring on the left and the new spring on the right.

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Reassembly should follow the reverse process. Be aware, the three casing screws are not evenly spaced and care should be taken to align the drive dog with the end of the camshaft.

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