Kurt,
Indeed, the headset to which you refer does use a series of smaller 1/8" ball bearings - just as did its clone brethren once offered by the likes of O.M.A.S., FT, Cobra, and of course the Colnago specific version. All of these component brands were made available at one time or another having either loose ball bearings or bearings with plastic retainers and either configuration can be used interchangeably. For a photograph of an O.M.A.S. labeled headset having the loose style of ball bearings, please refer to the following link detailing that which is installed in my 1983 Pino Morroni:
http://www.wooljersey.com/
While I do not have a photograph depicting one of these exact type of headsets having caged style ball bearings, I can offer the following image of a MAVIC 310 headset destined for installation on my Vitus 979 as its 1/8" bearing sets are identical to those used in an O.M.A.S. / FT / Cobra / Colnago components (...albeit construction of the MAVIC headset is decidedly different and therefore other of its various piece parts are NOT AT ALL interchangeable):
http://www.wooljersey.com/
As for the specifics of rebuilding your own headset, I would strongly counsel that you NOT re-use the original 1/8" ball bearings, but rather, replace them as a matter of course. If upon reassembly you still experience the "binding/grinding" you describe, then I would suggest the following:
OPTION 1 - remove and reinstall either your lower crown race on the fork or the lower head race from the head tube making sure so as to change its orientation relative to the other corresponding piece. The idea here is to realign these two parts so as to minimize opportunity for the individual ball bearings falling into pre-positioned wear points.
OPTION 2 - skip entirely the "tight-wad" Option 1 described above and simply replace the lower crown race as this is the singular piece part which is most likely to incur wear of the type that begets what I refer to as the "indexed steering" phenomenon. I happen to have several NOS spares on hand such that I can supply one should you desire.
OPTION 3 - in a similar effort to reorient the individual ball bearings relative to any wear patterns in the respective bearing races, convert from a loose ball bearing configuration to a caged version (...or visa versa if that had been the case). Again, I have several NOS sets of caged 1/8" ball bearings apropos your particular headset in the event you do not have another source for same.
You can contact me "OFF LIST" should you require any of the aforementioned rebuild parts.
Robert "occasionally accused of being headstrong" Broderick ..the "Frozen Flatlands" of South Dakota Sioux Falls, USA
-----Original Message----- From: classicrendezvous-bounces@bikelist.org [mailto:classicrendezvous-bounces@bikelist.org] On Behalf Of Kurt Wolko Sent: Friday, March 27, 2009 7:14 AM To: classicrendezvous@bikelist.org Subject: [CR] Colnago/Omas headset
All,
I am in the process of overhauling the headset on a '78/'79 Mexico and since I haven't done one of these in a real long time I thought it best to ask.
The headset is a Colnago, which from reading previous posts I am guessing is an Omas. There were 30 ball bearings on both top and bottom, 1/8 inch in diameter. Does that sound right? My copy of Sutherland's doesn't list Omas headsets.
The headset appears to be in decent shape, at least from my untrained eye. There is a small dark ring around the lower race on the steering tube. It doesn't have any pits that I could notice. Other than that, all the races and cups looked decent. I degreased everything and reassembled it with new grease, then began to adjust it by rotating the forks while lightly hand tightening the upper cup. Then I checked for play by pressing against the dropout, and continued to readjust until the play was negligible.
When the play is virtually gone, the headset feels like it's binding/grinding, and I'm pretty sure it's not supposed to feel like that. I reused the ball bearings, but maybe that isn't a good idea. Maybe I need to get some new bearings and try it out again.
I do have a super record headset I am thinking about using in place of this one but am not sure yet I have a problem.
Thoughts and comments are appreciated.
Kurt Wolko
Owings, MD