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post #34 of (permalink) Old 03-17-2019, 08:24 AM Thread Starter
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Chilblane's Avatar
Join Date: Feb 2018
Location: UK
Posts: 58
The hub was successfully extracted after the Cush drive removed. Now with better access the gap measured between the hub and face of the swing arm was at its worst 3mm varying axially as previously mentioned. Attached is an out of focus picture but you can just about see the gap. The hub surface condition is excellent. Swing arm bore surface generally the same save for some minor marks confined to approx 35mm long x 10mm wide at about 7 o'clock position (not easy to photo) Hub returned to swing arm after a couple of burrs were filed off the teeth, presumably caused by the force of the C wrench. Hub now hard up against the swing arm OK. Trial torque the hub bolts at 25Nm has now returned the slot in the swing arm to a parallel slot/gap. Finally pinch bolts then slackened and C wrench allows easy hub movement.

After cleaning up surfaces of the shaft and and hub there are signs of scorching on the sprocket side bearing. The sleeve of that bearing removed and its I/d varies by 0.08mm. Is that within tolerance?

The rear sprocket was cleaned up and the wear on the inner side is clearly variable, and is not flat when laid on a glass surface!

Chain alignment chain checks were not taken, as I think most would agree that the hub not sitting square in the swing arm bore is the cause of the problem.

If the tension bolts have been over torqued is it possible this could have damaged the hub body? I do not have a vernier large enough to check for any ovality.

If advice would be to replace bearings and seals in the existing hub, where are quality components available?

Of course the other question is how did the hub manage to be out of alignment in the bore of the swing arm (although now superfluous) interesting and maybe the distorted rear sprocket provides a clue?

Many thanks to everyone that helped me out of this jam (no pun intended)
Attached Images

2016 F4 RR mapped with ECU Studio
2017 Aprilia Tuono Factory
2019 F4 RC

Last edited by Chilblane; 03-18-2019 at 04:37 AM.
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