850 triple tree or fork yokes

I have my stanchions and triple trees (2 sets actually) in the shop for straightening, and plan to give them a sketch showing how the forks are not parallel to the steering axis.
Nortons are certainly not an everyday job for them nowadays so I'm concerned to think that they may attempt (and could succeed) in making them parallel, despite my sketch, inasmuch as it seems that Norton never published these specs.

Can anyone direct me (and them) to an authoritative source, other than this forum, which shows the steering rake at 28 degrees and the fork angle at 27 or less?
Thanks--
Rick

The Factory Workshop Manual frame diagram shows the steering head angle as 28 degrees.
How could this forum get it wrong with solid info like that !!
The 750 frame is also shown, labelled at 27 degrees.

The fork yokes have the fork tubes pointing 'backwards' slightly by virtue of the top yoke sticking out further forward - from the steering stem - than the lower yoke.
No matter how badly they try, no reputable shop can alter that - unless they cut and reweld them different !!

I have a rough old pic of the yokes viewed from above, back when I pointed this out to the NOC assembled throng.
Some of them flatly refused to believe it - until they held it in their hands, when it cannot be denied...
Take your yokes - out loose on their own - and view them from above.
This should be immediately apparent. Repeat as necessary, until you are totally convinced.
(They CANNOT be assembled any other way !!)

You can actually see this on bikes viewed side-on.
Especially if you stick a rod through the centre of the steering stem, and compare with the fork tubes.

BTW, the frame steering head angle of 28 degrees is the ONLY measurement which affects the steering.

The fork tubes pointing back (or forward) only affects the trail measurement.
It matters not one jot really whether the fork tubes are at 25 or 26 or 27 or 28 or 29 degrees,
it still only affects the trail measurement...
hth.

If the fork tubes require straightening I wouldn't even give the yolks to the shop doing the job (unless they are also bent) If the Commando yolks are bent then they are probably beyond repair, they are substantial items.

This shop has been in business for at least 50 years, and assures me that they can straighten all the parts. Frame Man in Sacramento.
They are recommended by Phil Radford, also.
They must have some serious muscle and measuring equipment, although they do not share any technique or even allow you into the workspace.
I'm headed out there this morning, try to get some reassurance.

As Rohan said, the 28 degree steering head angle is clearly specified in the 850 Commando service manuals, both in the specifications section and in the frame checking section. I've never seen anything from Norton that gives specifics for the amount of non-parallelsim (if there is such a word) in the yokes, and I've looked everywhere I could think of. But they are clearly bored at an angle. I have measured the difference in offset between the top and bottom yokes for my own interest. By my measurements, the offset in the top yoke is 2.780", and in the bottom 2.677". I measured the stock 750 yokes at 2.750" offset. Those measurements could be off by a thou or so, but not much more. I realize this is not the factory info you are looking for, but I'm throwing it out to point out that the difference is obvious, so there should be no question about whether the 850 yokes are bored at an angle.

As gripper said, unless your forks and yokes have been in a serious accident, it is unlikely that the you need to worry about the yokes. If, when you bolt everything up in the proper order, a pair of straight tubes fit easily and are parallel and equidistant, the yokes are good. I'm sure the Frame Man can check that everything is true without needing the factory specs for the yokes.

Ken

lcrken said:

As gripper said, unless your forks and yokes have been in a serious accident, it is unlikely that the you need to worry about the yokes. If, when you bolt everything up in the proper order, a pair of straight tubes fit easily and are parallel and equidistant, the yokes are good.

Click to expand...

AND, the front wheel points true and straight ahead.
Then you know they are good.

Hi Mr.Rick, There is always the aftermarket for a replacement. As in cNw or NYCNorton.

Thanks to all who commented. Just as a follow-up: I picked up the parts yesterday, $220 (cash only) to straighten 2 stanchions and 2 sets of trees.
$35 per tube, $65 per yoke set, $20 to pull the sliders off and remove the damper assemblies from the forks. Shoulda done that myself!
He (Pat, who's worked there for more than 20 years) told me one stanchion was more than a millimeter out, the other not as bad, but not right. About the yokes, he said only that they had suffered some "torsional stress", are now straight, and he didn't need the info I had provided regarding the 1 degree difference. Then he made a copy of my sketch for himself.
I'm pleased to have done all I could to make things right, but would have liked to receive a more detailed report about their condition, and an idea of what they consider "out of spec" for both the tubes and the yokes.

Tomorrow I'm on a different project altogether, but wd like to ask another question:
REmoval of the top yoke was a bash job from below. Is there a trick to re-fitting them, that might use a smaller (or no) hammer? I have it in the freezer already, and worry about displacing the bearings while driving the stem of the upper yoke back into position.

I just did this and as long as the bearings are square in the neck they should ease right in with a slight tap at most. I was more worried about condensation on the stem forming rust.

Smart move that you gave the guy the yokes too... thanks for reporting back.