View Full Version : Started a new XS650 build, frame is custom having trouble finding neck bearings.

03-03-2017, 9:42 PM
Howdy all.

Picked this up from a fella at a swamp meet. The front end as far as I can tell by the forks is from a KZ650, it came with just a stem in the trees and nothing else.
The stem is originally a KZ650 on the trees, it's at the shop which is out of town so I can't grab the measurements on it at this very moment for the bearing ID but here's the neck tube...



Inside the neck tube you can see theres a stopping surface for the bearing to seat against, my question is where do I even start to look for a stem bearing that would work for this? I can't seem to get the ID of a stock KZ650 bearing anywhere

03-03-2017, 11:15 PM
You need neck cups for your bearings. The bearings don't go in the neck is self they sit in cups. Your stem should be 7/8 if I'm not mistaken

03-03-2017, 11:20 PM
The stem is burly, far burlier than my XJ650 which made me think 1", I'll have to measure it to be certain.

Alrighty, so I need to source neck cups, this is new territory so forgive me if I come off as dumb but where does one even start? Typing "1.88" neck cup into the google" is bringing up all sorts of weirdness. Basically at 1.88 I figure I need a 1 7/8 OD neck cup, I might be getting a set of 78 FXE forks and trees here as well to replace the KZ's, if they're both 1" necks it should work yeah?

I should just machine the fuckers myself.

03-03-2017, 11:26 PM
No worries man.

If it's a 1 " stem any harley neck cups and bearings will work. Although you might run into issues with height of the stem not being tall enough for your top clamp and a nut.

03-03-2017, 11:36 PM
What a frustrating thing this is, googles absolutely killing me because typing in any measurement brings up a hundred websites about doing stem conversions, nothing about finding an OD for neck cups, hop onto JP cycles they don't even list OD, just fitment.

This is basically whats on the front of the bike right now, http://i.imgur.com/Cpy8TQl.jpg

But the websites I'm usually buying parts from are being kinda wank "Fits FLHTXTWG Wilford G Edition" does not chooch in this regard.

Any ideas to even get a whiff of an ideas fart on this one?

03-03-2017, 11:40 PM
The neck cup thing, are you sure? The only reason I'm asking is because it's got that ledge machined into er right there, would this not work? Basically the first part rests on the lipped edge in the neck so the top of the bearing sits flush with the 2" tube.


03-03-2017, 11:54 PM
I guess it could be a custom piece but I've never seen anything like that before. The object the beating sits in is the race. Can you get the dimensions for the race? See if that will fit in your 1.888 neck

03-04-2017, 12:05 AM
Actually, dropping in a tapered roller bearing from timken works in those dimensions.

Timken has the 32005X tapered roller bearing, the OD is 47mm so 1.85 of an inch, v.s. 1.88, so the neck tube above that machined in ledge is only 0.03" bigger so it'll slip right in there no problem. The ID of the bearing is 25mm so 0.98" a different of 0.02" on the neck stem. So where the bearing race sits in the neck tube, it's 0.03" of play, or about 700 micrometers, so thats about.. 2 dust mites in length, on the ID, only 1 dust mite.

I totally used dust mites as a unit of measurement.

03-04-2017, 12:28 AM
Well there you go give that a shot