harleyKmodel

28 or 30? Book says 30 (15/15). I found 28 (14/14) in a ‘62 that looked like it had never been apart. I’ve always used 30 5/16” bearings, but the ‘62 with 28 seemed very happy.
Any insights on the right number?

5/16 always, since the first of that neck size began in the '30s.

The reality is that while there should be room for 15 . . .sometimes only 14 fit correctly.

Of the last 5 bikes I've done -- 4 took 15 balls top and 15 bottom . . but one came apart with only 14 and went back together with only 14 a side.

chuckthebeatertruck wrote:The reality is that while there should be room for 15 . . .sometimes only 14 fit correctly.

Of the last 5 bikes I've done -- 4 took 15 balls top and 15 bottom . . but one came apart with only 14 and went back together with only 14 a side.

So true, and machining tolerances on parts particularly through the '70s deteriorated to a point where only a few thousandths out of tolerance on a radius creates a big difference in available clearance. However, 1/4 inch balls on a 5/16 radius are never a good plan. The contact area diminishes dramatically.

I am about to rebuild (gain) my neck bearings on my 55 KHK. I have been suggested in the past to change out to Timken bearings. SOOOO, has anyone on here done that and what was the procedure and results?

Thanks,

Mayday

change from 15 to 14 each happened around 65.
either one seems to work.

timkens- id pass on that idea.
usually dead soft frame cups.
and
no spherical interface between top cone (inner timken) and tree stem.

the frame bores often were misaligned. so the upper oe spherical interface was important to the road feel of these bikes.