Yalla! Headset Assembly
The Yalla! comes with the headset cups already installed in the frame. Included in the box are the other pieces of the headset. Not included in the headset is the star nut, bolt and top cap.
When building your bike up, you'll need to assemble them in the correct order to ensure proper function of the headset. The image above shows the correct order of the parts.
Make sure to apply grease to all contact surfaces in the headset, like between the bearings and the cups, crown race and compression ring. It's not good to have grease all up your steerer tube for the rest of the fork assembly, so give the steerer tube a wipe to remove excess grease before you install the rest of the fork.
The headset bearings are angular contact, so when assembling the headset, make sure the angled surfaces of the bearings match to the angled surfaces in the headset cups. The top and bottom bearings are the same.
It's easier to install the bearings in the cups first, then install the plastic shield into the lower cup before installing the fork into the frame. That way you can make sure the plastic shield is installed properly and sitting up against the lower bearing.
The top cover of the headset includes two seals. There is an o-ring on the inside diameter, to seal against the steerer tube of the fork, and a lip seal on the underside, to seal against the top cup. Make sure these seals are installed correctly in the top cover during headset assembly.
It is also possible that your headset will develop a small amount of play after the initial ride. This is completely normal as all the parts settle into their final position. Simply re-preload the headset if this happens and torque all bolts back to spec and carry on riding.