Headset/front fork play - threadless fork/stem

[Markie76]

Hi Guys,

I bought a used GT Aggressor which needs some tlc.

I last owned a bike some years ago but do my own car/motorbike servicing and know how to use a spanner so am up for it.

My first job is to eliminate the play in the front fork/stem - which seems bad/excessive - 4-5mm - if moved forcefully there is like a dull thud.
However, his bike has a threadless fork/stem which I haven't ever worked on before and any advice would be much appreciated.

I have undone the handlebar pinch bolts and removed the top cap & handlebars & spacers (2 large & 1 small).
I then taped the stem until it started to come out the bottom.
There are 2 caged bearings (20 bearings in each) and they have some wear - some look perfect.
The bearing races also look ok - the cups in the frame (upper & lower) have a shiny smooth ring and the cones (on fork & top race) again have a shiny ring but a few specs of odd wear.
I went down the cycle shop with all the removed bits - they didn't have complete caged bearings but I bought new ball bearings.

I carefully replaced the old caged bearings with new ones and did a test fit lining everything up, replacing the dust covers & centering sleeve and tightening the top cap.
BUT there is still some play - less than before but still present. I tried again pushing down while tightening up - still the same.

What haven't I done?
What could it be?
What to try next?

Thanks,

Mark

 

[RecordAceFromNew]

I tried again pushing down while tightening up - still the same.

This is the issue. The top cap is nothing more and nothing less than a preload adjuster - you need to ensure the top of the stem (or spacers if they are above the stem) is a few mm higher than the top of the forks steerer, and gradually tighten the top cap (while leaving the rest of the stem bolts loose) until the play is taken out while the headset bearings are not binding, then tighten the two horizontal stem bolts to keep the position. For details see this.