In this article I’m going to explain how to overhaul a vintage mountain bike headset and its bearings.
I was lucky enough to be able to buy a Koga Miyata Skyrunner Carbolite. But, as is often the case with bikes which are 3 decades old, the bike is in need of some love.
The bike is from 1991 and comes with a for the time top-of-the-line Shimano Deore XT groupset, including the headset we’re going to look into.
The previous owner said the headset had issues. When I came to pick up the bike he told me a bearing had split, and his father had removed it.
I had never heard of something as a split bearing. And as it turned out this wasn’t the case. So I’m not going to repair a caged bearing. But I am going to give you a couple of pointers when overhauling a vintage mountain bike headset yourself.
Video Tutorial
Step 1. Loosening the front brake cable
Before you can open up the headset you’ll need to remove the stem. And before you can remove the stem you’ll need to loosen the front brake cable. Since the brake cable is pulled taut you won’t be able to pull the stem upwards otherwise.
The Skyrunner has a Deore XT cantilever setup. This means you can loosen the right side by hand, but you’ll need to loosen a bolt on the left side to release the cable. I put the bolt back so I don’t lose it.
Step 2. Removing the stem and handlebars
removing dust cap 
The vintage mountain bike headset is a threaded headset. It means the top of the fork has a threaded part onto which you screw the headset.
Unlike newer setups the stem is inserted into the steerer tube. A wedge located at the bottom of the stem is forced against the inner wall of the tube when it’s being pulled up by rotating the large bolt inserted into the stem.
Because this wedge is often seized and/or corroded into the steerer tube you’ll need to give the bolt a solid tap with a mallet so the wedge loosens.
quill stem wedge still in steerer tube 
hanging handlebars against frame
Afterwards it should be easy to remove the stem. Since all cables are still attached to the handlebar, you can’t move the stem entirely, but you’ll need to gently hang the handlebars from its cables.
Step 3. Removing the headset and bearings
After removing the stem you have clear access to the headset. The headset has an upper bearing race which is tightened onto the bearings by screwing it into place.
To keep it there you have a lock nut that is screwed on top of it, just as a cone nut of a hub axle is kept into place.
A thin washer sits between the lock nut and upper bearing race. The washer has a tiny lip on the inside so it can only be placed in one way onto the steerer tube.
Underneath the upper bearing race are the caged bearings (sometimes the cage is referred to as a retainer).
Between the bearings and the crown race sits a very thin plastic seal. It’s concave to fit snugly against the bearings and has an edge underneath that fits just over the crown race.
After I cleaned the crown race I saw evenly spaced dents. I had never seen such damage before. The dents corresponded with the amount of bearings.
Step 4. Cleaning the vintage mountain bike headset bearings
The easiest and fastest way to clean any bicycle part is using white spirit. Cleaning the vintage mountain bike headset bearings is done by putting them into a plastic jar, submerging them, and swirling the container for a couple of minutes.
The white spirit will dissolve the grease leaving you with very shiny headset bearings.
I also cleaned the upper bearing race and inspected both the race and the bearings, only to find nothing out of the ordinary. The bearing race wasn’t pitted and the bearings seemed to roll smoothly and didn’t show any signs of wear either.
Step 5. Putting the headset back together
If your vintage mountain bike headset shows signs of rust and has little or no grease left, it’s much more likely you’ll encounter damage. I didn’t see any of that and concluded the bearing race simply was screwed on way too tight, causing the bearings to bind into the race.
Remember, bearings simply need to be kept into place to function. They’re not nuts and bolts which need to be tightened. Simply tighten the bearing races until the bearings don’t show any signs of play anymore.
I re-greased the bearing race and bearings and screwed them back into place. Make sure the seal sits properly, with the concave side facing up.
Step 6. Testing headset for signs of play
After you’ve reinserted the stem and handlebars you’ll need to tighten the bearing race in such a way so that the headset no longer shows any signs of play, but still rotates smoothly.
This particular headset requires a massive 38mm. headset wrench to tighten. Since I don’t have such a tool I use my Park Tool adjustable wrench.
The disadvantage of not having a specific headset wrench is that when you tighten the lock nut, you sometimes over-tighten the bearing race with it, because you can’t keep it in place and it rotates with the lock nut.
You also can’t tighten the bearing race with the lock nut on top since the clamp of the adjustable wrench is too thick and touches the lock nut which sits atop the race.
If you’re happy with how the bearing race sits and how the handlebar rotates, you can test it for signs of play by using both brakes and pushing your bike forward using the handlebars.
If the headset still has play you’ll clearly see it move on top of the steerer tube. Adjust the race accordingly until the play is gone.
And that’s how you overhaul your vintage mountain bike headset bearings.
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