All Balls tapered bearing conversion pre-1979 machine work?

[Chuck78]

http://www.allballsracing.com/media/installation/SuzukiStemmod2.pdf

In the All Balls instructions with my tapered steering roller bearing conversion kit, it says that on pre-'79 Suzuki's, " It may" be necessary to modify the steering stem according to their sketch.



It shows 10mm of machined area between the threads and the larger area of the stem. It shows having that area lengthened in a lathe to 16mm.

Well, I have just read of other people on here with 78 or 79 Suzuki's that theirs went together without having to do any machine work. Measuring my spare 78 gs750 stem, I have 13mm of flat machined area before the taper up in diameter to the lower larger diameter area. There are also a few mm of smaller diameter area above the machined surface but below the threads, where it looks like they just didn't machine the threads down all the way to the bearing's surface. If I include the taper below and the unthreaded area, I get just about 16mm. Any clue if my 13mm machined area will be plenty? The list of bikes this bearing conversion kit works for goes all the way back to the early 70's with DR's and GT's etc... So I am wondering if the GS is an exception, or at least this 78 stem that I am trying to swap to my 77?

I was about to swap my bent lower triple before a 700 mile road trip, but with only two evenings to go (and needing to do fork seals at same time), carb work, & packing, maybe I will just continue to ride the rest of the season with slightly crooked handlebars and leaking 1 year old bikemaster fork seals if tearing the bike down will mean required machining.

[Chuck78]

Not sure how All Balls measured, but their drawing really is generic to fit many applications of Suzuki's, and that is probably why they cant give any measurements from the bottom of the stem to the bottom of the area needing to be machined for the upper inner race.

Here is 16mm on my calipers, as they specify, but on my stem, that means measuring the taper up to the un-machined non-bearing surface as well as the step down above there where the threads aren't cut all the way. Anyone else have the same measurements and had theirs work out or not work???

16mm on calipers:

[Chuck78]

13mm on calipers, the full length of useable machined upper bearing inner race surface:

[witttom]

Subscribing to thread.

[allojohn]

If you choose not to machine the stem you will have 3mm less for the stem nut and dust cover........like mine!
My front end certainly feels stable and the stem hasn't loosened in 2 years, so I'm happy!