Get in the garage and fix that drip
When changing fork seals the stanchions will need to be removed from the chassis, so place the bike on stand that will allow the frontend to be free. The most secure way to do this is using an ABBA stand which supports the bike from the swingarm pivot points. Tether the back end of the bike down so that the front wheel is in the air.
To maintain your steering geometry, measure how much the forks protrude through the top yoke using a Vernier or steel rule. Also make a note of handlebar position if they are the adjustable type by marking the clip-on with a pen. Then loosen the fork cap by half a turn, because it will be easier now than doing it later when it’s off the bike.
Remove any items, such as the mudguard, that prohibit access to the fork pinch bolts and the forks’ subsequent removal, making sure that you lay each part out in a logical order for ease of reassembly. Loosen the spindle nut then the pinch bolts before removing the front wheel and any items that are attached to the forks, such as brake hose clamps.
Loosen the pinch bolts on the top yoke and handlebar clamp – there is no need to remove them completely. Loosen the bottom yoke bolts and, as you free the last one, support the fork leg with your other hand in case it falls out and is damaged. If the fork is still a bit tight in the yoke, try removing it with a firm downwards twisting action.
Make sure you have a tray to drain oil and plenty of cloth or workshop paper towels. Secure the fork leg in a vice using soft jaws. Begin to remove the pre-loosened fork cap and be prepared for the spring to pop it out. Remove the spring and any spacers then upend the fork to drain the oil.
Undo the Allen bolt at the bottom of the fork leg, this retains the fork stanchion, let residual oil drain as you do so. Gently prise out the dust seal and remove the clip that locates the fork seal. The leg and stanchion can now be separated. Remove the seal from the fork leg with a suitable lever.
Spend some time cleaning all the individual components, wipe away dirt and grime and inspect for damage. Look closely at the fork stanchions for any signs of pitting, they can be dressed down gently with 800-grade wet and dry paper to clean it up. Give the interior of the fork leg a good blast with brake cleaner then make sure it is completely dry.
Fit the new seal facing the correct way up, making sure any washers / spacers are in place underneath. Ideally, the seal should be installed with a fork seal driver but if you don’t have one then it can also be done using a blunt drift – a suitably sized socket makes a good tool. Make sure it goes in square until the retaining groove is visible.
Re-assemble the fork stanchion to the lower, and then fit the bottom retaining bolt with the washer. Check the manual for the correct type/grade of oil and the specific amount required after a rebuild – usually it needs to be measured without the spring fitted. Pour in the oil and then pump the stanchion to make sure that there is no trapped air.
The manual will list the air gap – the space between the top of the tube and the oil level – usually measured with the fork fully compressed with no spring or spacer. Measure it using the proper tool or a steel rule, then adjust oil as necessary. Refit the spring and spacer then refit the fork cap tight by hand, reinstall in the bike then tighten up the caps to spec.
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