HarleyTechTalk

In order to install a 1980 Sportster front end on to a 1970 Sportster do I need to replace the neck cups?Any thoughts?

https://www2.vtwinmfg.com/fork-neck-cup-conversion-kit.html

Thanks for the reply but my question is are the necks the same size or do I need to change something to make it work.

No the stem in the front end is not the same. That's why I posted the link to the conversion parts.

These also work.


Vulcan

Ok got it! Thanks for the reply

Can't you use the 1970 lower tree?  You can use the original brgs then.  IIRC I used an early FX lower tree and post to mount an early XLCR dual disc front end on my early shovel head frame.  It worked great.

'57 to '72 Sportsters use a 1.312" fork tube. '73 to '86 uses 35mm (1.378") fork tubes.

Late forks won't fit early trees, hence the conversion kits. 

Ahhhh.  I used a 77 XLCR front end and I don't really remember what year FX lower tree so there you go.  :nix

'73 to '83 FX used 35mm tubes. All Big Twins used Timken bearings at the tree.

'52 to '77 Sportsters used ball bearings at the tree.

Yup, and that's why it worked.  We did a few like that. Mine was the only XLCR conversion in the bunch. The IIRC Timkin  07100 brg set (same as the swing-arm). It was a long time ago.

If you're  doing  an upgrade  I'd  change  cups  and  bearings while  you  have  it  apart  just  for  piece  of  mind .