OK, this may not be the definitive method, but may be of help to anyone who is daunted by the prospect of taking a spanner to their bike. If I've missed anything, please feel free to ridicule me.
My S1 has 24,000 odd miles on the clock and to be honest, I didn't think that the bearings were bad, but after 12 years, it had to be worth spending a few hours and £20 worth of bearings for peace of mind.
Thanks to Tubbs and Moorespeed Racing for his patience, all parts and facilities.
First of all, you need to make sure that the bike is well supported in an upright position. If you haven't access to a proper work ramp, use a paddock stand to support the rear end. Then use a jack and wood under the front of the engine to raise the front wheel off the floor. Ensure that the set up is rock solid. If you've got a work ramp, use ratchet straps to tie the bike down.
Remove the seat and petrol tank.
Remove the brake pads from the caliper to give plenty of room and then remove the 2 bolts holding the caliper to the fork leg. Carefully remove the caliper. Be patient, it's a tight fit with only minimal clearance on the wheel rim.
Once clear, use cable ties to secure it out of the way.
Have a fag.
Next, remove the front mudguard..........
Then remove the wheel.
Loosen off the headlight clamp pinch bolts then, one side at a time undo the fork clamp Allen screws. This will allow the fork legs to slide down through the yokes.
The headlight unit will now be dangling in fresh air so use some cable ties to secure it to the handlebars each side.
Now that the fork legs are clear, undo the top yoke pinch bolt and loosen the large stem bolt. As you loosen the bolt, you can give the bars a bit of a wiggle to loosen the stem. Support the bottom yoke with one hand and fully loosen the stem bolt, then twist the bottom yoke free.
If you are working on your own, it would be a good idea to support the top yoke from above using a bungee or string. If the top bolt is not removed fully, it will allow the yoke to rest in the frame, but it will be in the way later,when you drift out the outer bearing races.
That's not rust, it's the colour of the grease.
Use a bearing puller to remove the inner race from the stem.
Use a large diameter bar to tap out the outer races from the headstock. Work evenly on the bearing lip, so as not to bruise the headstock.
Both outer races were in fact quite worn.
Hard to pick up on camera (well mine anyway) but they definitely needed replacing.
Give the bottom yoke a good clean with solvent.
.........And also the frame headstock.
Clean off the preservative oil from the new bearings using solvent before fitting. Don't forget the base washer.
Lubricate the new bearing with good quality grease.
Do the same for the upper race.
Tap in the new outer races. These sit under flush to the frame so ideally it would be good to use an alloy billet, slightly under the O/D of the outer race to send it home.
If you do not have access to a lathe (or mate with one) then an appropriate size socket will suffice.
Insert the stem into the headstock and drop on the upper bearing. Refit the top yoke and nip up the stem bolt so there is no slack, but do not tighten up yet.
Clamp the fork leg in a vice using some cardboard to protect it and undo the top nut.
Invert the fork leg over a container and drain out the old oil. Allow time for as much as the old stuff to drain as possible.
Have a fag.
Service the fork legs as per the manual instructions.
Use the vice again to refit the top nut.
.......One fresh fork leg.
Slide the legs back in the forks one at a time. This can be a bit tricky. Ensure that the headlight clamps are square to the leg. When they are through and flush with the top of the upper yoke, nip up the upper clamp to hold it in position.
Once both legs are in, you can tighten up the stem nut and pinch bolt.
You can do it by the book or you can do it by feel. Either way, you'd be wise to check it again after a few hundred miles.
Tighten up the fork clamp Allen screws.
Refit the front wheel. It's also a good time to check and lube the speedo drive, as this gets full of road crud.
Refit the brake caliper and pads using some copper slip on the back face of the pads.
Refit the mudguard.
.......And the tax disc......
Finally, re tighten the headlamp brackets, ensuring that they are even.
Have a fag.
Start the bike, gun the motor twice and head for the Twisties.