Project Big Bore

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Step 6 : Measurements are taken and construction of the swinging arm start. I am going to reverse the

way the NSR 80 swinging arm is put together by putting the bearings in the frame rather than the swinging arm.

Firstly I am making the bearing housing to replace the current swinging arm tube that is on the 90 frame.

This is the picture of the current setup on the NSR. The bearings sit into the Swinging Arm.

NSR Swing Arm Setup

Turning a new swinging arm pivot with recesses for a push fit of the bearings. This will be welded into the Cub 90 frame.

Turning New Swinging Arm Pivot New Swinging Arm Pivot

New setup (Bearing not pushed in flush), and the swinging arm bush left 1.5mm longer

Swing arm pivot assembled pivot bush left 1.5mm longer


Step 7: Making the jig for the new swinging arm. This was very slow and painstaking. Measure, measure and re-measure.

Swing Arm Jig Swing Arm Jig


Swing Arm Jig Swing Arm Jig


Step 8: Making the stainless steel eccentrics for the back axle to adjust the chain. It will give me 18mm adjustment.

Boring holes for eccentrics Finished Eccentrics


Step 9: Making the Eccentric Houses and Bushes for the front of the swing arm

Eccentric Houses Swing Arm Bushes


Step 11: Best Laid plans and still had to widen the jig. Then bending the steel for the swinging arm

Whiteboard Swinging Arm Tubing


Problem 3: Axle too short. Extra 30mm needs to be added.


Problem 3 Solution: Cut / Pin with Roll pins / Weld / Turn down in the lathe

Rear Axle cut to pieces Rear Axle Modified


Step 12: Turning out 28mm hole for front bush. Swing arm roughly in place.

Turning out swinging arm hole for bush Swinging Arm mock up

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