850 yokes on 750 frame (yet again)

baz · Apr 24, 2018

Having read quite a few threads on this matter ie the 850 (Ang) yokes made for the 28 ° frame are de raked by one ° and should not be used on the 750 27° frame etc I have a specific question
Has anyone actually tried this?
And what did it do to the handling?
I have fitted many different forks/yokes with different offsets to many different bikes, including raked yokes but what happens with a de raked yoke??? Cheers

kommando · Apr 24, 2018

The NOC Commando notes cover this and recommend only mixing 750 yokes with an 850 frame and dire warnings about the other way round, no idea if it's right or wrong. Its been covered in a very long thread in the past and rather than rehash that you had best find and read it but apply a flame suit as it went like an oil thread.

74ok · Apr 24, 2018

i did come across some posts commenting on mixing..

i ended up commenting once recently in a sump on off valve thread, i actually didn't know it was a hot button, something that can easily occur with new folks,

revisited topics sometimes brings a better fresh condensed perspective to the forefront,

long threads without conclusions or summations can also be confusing,

ideally, there is a short accurate summary that is also an easy link

delagem · Apr 24, 2018

Somebody ship me a set of 850 yokes and I'll give them a try, and report back (assuming I survive)...

74ok · Apr 24, 2018

https://www.accessnorton.com/NortonCommando/split-topic-triple-trees.5369/

https://www.accessnorton.com/NortonCommando/71-frame-and-steering-yokes.3324/

https://www.accessnorton.com/NortonCommando/rake-and-trail-specs.10734/

https://www.accessnorton.com/NortonCommando/peter-williams-fork-yokes.22404/

baz · Apr 24, 2018

This is the reason for my specific question,
"Has anyone tried this" I have read most of the theories/warnings etc

74ok · Apr 24, 2018

i'd say important to be aware of
https://www.accessnorton.com/NortonCommando/split-topic-triple-trees.5369/page-2#post-57635

L.A.B. said:
OK, fair enough, but for safety's sake I hope any of our members who may not have been aware there is a potential problem will have taken note.

Quote from the Commando 750/850 Workshop Manual:
"Front Forks/Steering
Section G

"Note : 850 models use a special pair of yokes identified by "ANG" stamped on lower surfaces of both yokes. These yokes must be used for 850's and must not, under any circumstances, be interchanged with earlier types".

74ok · Apr 24, 2018

dunno if there is more info on this
https://www.accessnorton.com/NortonCommando/split-topic-triple-trees.5369/page-2#post-57645

rvich said:
So it appears that I have 750 yokes on an 850 frame. From the above it sounds as tho mixing the two is the worst case scenario due to misalignment of the tubes. When sighting past the headstock on the bike in relation to the fork rake, mine is wider at the top, thus reducing trail. I am still trying to decide if I should hunt up the 850 yokes.

https://www.accessnorton.com/NortonCommando/split-topic-triple-trees.5369/page-3#post-57671

debby said:
It turns out I have a set of 1971 750 triple clamps on my 850. Don't know where those came from, probably some previous owner supplied them. The bike does seem a bit "twitchy" at highway speeds compared to my 750. I was thinking that it was ok to run 750 triples on an 850 frame, but if it reduces trail that doesn't sound good. I do have a set of 850 triples that I'm planning to put on that bike. Just have to get them powder coated first.

but the question is 850 yokes on 750 frame ride reports
https://www.accessnorton.com/NortonCommando/split-topic-triple-trees.5369/#post-57628

Danno said:
I have ANG on one clamp on the bike and ANG on the other in a box. My bike (titled as '71) was originally restored and updated with MkIII power train and running gear in 1984 and ridden until 1994 when it was put in storage.

measuring
https://www.accessnorton.com/NortonCommando/split-topic-triple-trees.5369/#post-57616

Danno said:
the difference in the geometries is in the steering neck itself, not the trees. The trees are dimensionally the same; Same center-to-center measurement on the tube clamps and same offset from the steering axis to the clamp centers.

in agreement
https://www.accessnorton.com/NortonCommando/split-topic-triple-trees.5369/page-3#post-57658

grandpaul said:
The clamps can't be mixed IF YOU ARE WANTING TO RETAIN ALL ORIGINAL FEATURES exactly as they were on the orignal bike.

Other than that, if you don't need the mounting provision for the idiot light panel, and if you don't need the identical steering lock setup (I NEVER use steering locks), then it matters not one whit.

Danno said:
Thank you. I have been trying to tell everyone that, but some seem to think there is an extra smidgen of rake built into the trees. All 4 trees have the same offset (distance center-to-center from the steering neck to the fork tubes.) Does anyone really believe they would build a degree or two of rake into the yokes to compensate for an extra degree of frame rake when the crankcase boring bar had to be wedged with a 2x4 to keep the main bore alingment concentric with the cases? Get real.

baz · Apr 25, 2018

Blimey there's more threads on this subject than I had realised!
I shall have to read through and see if anyone has actually tried it,
Cheers

74ok · Apr 25, 2018

thought this meant running mklll forks on a 71 frame for 10 years

https://www.accessnorton.com/NortonCommando/split-topic-triple-trees.5369/#post-57628

Danno said:
If that's true, it shoots a hole in your theory that the clamps can't be mixed. I have ANG on one clamp on the bike and ANG on the other in a box. My bike (titled as '71) was originally restored and updated with MkIII power train and running gear in 1984 and ridden until 1994 when it was put in storage.

L.A.B. · Apr 25, 2018

grandpaul said: ↑
The clamps can't be mixed IF YOU ARE WANTING TO RETAIN ALL ORIGINAL FEATURES exactly as they were on the orignal bike.

Other than that, if you don't need the mounting provision for the idiot light panel, and if you don't need the identical steering lock setup (I NEVER use steering locks), then it matters not one whit.

Danno said: ↑
Thank you. I have been trying to tell everyone that, but some seem to think there is an extra smidgen of rake built into the trees. All 4 trees have the same offset (distance center-to-center from the steering neck to the fork tubes.) Does anyone really believe they would build a degree or two of rake into the yokes to compensate for an extra degree of frame rake when the crankcase boring bar had to be wedged with a 2x4 to keep the main bore alingment concentric with the cases? Get real.

We "got real" further into the thread as the ANG yokes are "raked".

Danno said: ↑
If that's true, it shoots a hole in your theory that the clamps can't be mixed. I have ANG on one clamp on the bike and ANG on the other in a box. My bike (titled as '71) was originally restored and updated with MkIII power train and running gear in 1984 and ridden until 1994 when it was put in storage.

Once again this is out of context and not accurate as subsequently proved by debby later in the thread.

https://www.accessnorton.com/NortonCommando/split-topic-triple-trees.5369/page-4#post-57683
Edit:

064084 850 upper: 72 mm
064083 850 lower: 69 mm

064083 is approximately 65mm according to my own measurement.

One ANG and one non-ANG yoke cannot be "mixed" as in used as a pair because the ANG upper and lower yoke offsets are unequal and the stanchions if fitted through the lower yoke won't line up with the upper.

Danno · Apr 26, 2018

I can't doubt your word, Les as 99 and 44/100reths% of the time you are spot on, but I can't for the life of me figure why they would rake the frame by 1 degree and then get it back by de-raking the yokes. Does the trail end up significantly changed? Maybe some sort of lessening of required bar leverage? Just seems like a lot of hassle for nothing from a company that was already circling the drain.

kommando · Apr 26, 2018

From the NOC notes

Page 12

FORK YOKES: 750 - - Engine Nos. 221545-221644 and 230536-230685, 850 all.
All these had the revised steering
geometry by new (850) frame
064140. Also new fork yokes
004078 (lower) 064080 (upper
with stem) the yokes must be
used in pairs. Do not mix old
and new ones. The factory release
states also do not fit old
yokes to late frame or vice
versa. T.R.S. states this was
due to lack of knowledge of the
effect. See Page 24

Page 24

In any case where a new frame is needed 1 would recommend the early 850 type frame (although the
change-over is a bit complicated for a pre-1971 model with Featherbed-type yokes and adjustable
steering bearings). The steering is more positive at high speed with 850 geometry, but to get the greatest
benefit you also need the 850 yokes (but the 750 type will fit and give the desirable increased trail).

You only really get your head round this by drawing the 2 schemes out on paper and looking at the differences.

o0norton0o · Apr 26, 2018

I get my head around that no problem because there's an increase in trail which helps the bike be more stable overall (at the cost of some high performance handling), but as Danno said, I can't get my head around why Norton would increase the head angle, then put some rake on the yokes themselves to bring the trail numbers back to where they originally were... That's the perplexing question...

Perhaps there's a reason that virtually the same amount of trail arrived at in these 2 different ways has different handling qualities. Perhaps some racer will chime in and propose an answer....

kommando · Apr 26, 2018

The changed head angle provides the extra stability with an unchanged trail, you have to continue the headstock angle out along an imaginary line to see where it finishes.

L.A.B. · Apr 26, 2018

Danno said:
I can't doubt your word, Les as 99 and 44/100reths% of the time you are spot on,

It's the second time you've tried to hang this on my shoulders as if it's somehow my idea instead of established fact and the numbers don't lie.

If we go back to what you said in the "Split topic" thread.

Danno said:
750 bottom clamp 064083

750 is 061916 however, some late 750s were built using 850 frames therefore they had 850 ANG yokes (see kommando's previous post).

Danno said:
750 top clamp 081017

061917 ?

Danno said:
850 bottom clamp 08 (the rest was wiped out by the drilling for the brake line fitting)

Perhaps you read 06 as 08 or the 08 from 064083.

Danno said:
850 top clamp 065721

The 750 bottom clamp and the 850 top clamp are both stamped ANG

If the bottom yoke/clamp was indeed marked 064083 ANG then it's an 850 frame yoke.

850 (Mk3) I think most would agree the forks are not parallel to the stem/steering axis.

Here is a 750 frame lower yoke 061916...

And then with an 850 064083 ANG lower yoke placed on top, back to back in line with the 750 yoke...

The difference. The other side is the same so it isn't just a few thousanths of an inch...

850 Mk3 yoke also 064083 ANG again back to back with the 750 yoke, same result...

Therefore it seems reasonably obvious that ANG and non-ANG yokes can't be used as a pair.

74ok · Apr 26, 2018

for the thread question, can 850 yokes be used with earlier 750 frames? the later 750s being simillar to 850s

i think this post confirms it has been done, depends tho what "updated mklll running gear" means
https://www.accessnorton.com/NortonCommando/850-yokes-on-750-frame-yet-again.25103/#post-373141

Danno said:
My bike (titled as '71) was originally restored and updated with MkIII power train and running gear in 1984 and ridden until 1994 when it was put in storage

baz · Apr 26, 2018

I was hoping someone would say they'd tried the 850 yokes on a 750 frame either by accident or by design
I'd love to know what happens to the bikes handling
As a footnote I can't see how anyone would be using an 850 top yoke with a 750 bottom or vice versa
If I ever get time I am going to try an 850 set of yokes on my 750 commando just to see what happens to the handling, cheers

74ok · Apr 26, 2018

i'm not clear on this late 750s part,
"FORK YOKES: 750 - Engine Nos. 221545-221644 and 230536-230685. All these had the revised steering geometry by new (850) frame 064140

Also new fork yokes 004078 (lower) 064080 (upper
with stem) the yokes must be used in pairs. Do not mix old and new ones."

are these yokes angled like on the 850 ang type? must be a reason for
"must be used in pairs. Do not mix old and new ones"

then
"The factory release states also do not fit old yokes to late frame or vice
versa. T.R.S. states this was due to lack of knowledge of the effect. See Page 24"

looks like there is some info out there using 750 yokes on 850 frames

is there a link for the noc info?

kommando said:
From the NOC notes

Page 12

FORK YOKES: 750 - - Engine Nos. 221545-221644 and 230536-230685, 850 all.
All these had the revised steering
geometry by new (850) frame
064140. Also new fork yokes
004078 (lower) 064080 (upper
with stem) the yokes must be
used in pairs. Do not mix old
and new ones. The factory release
states also do not fit old
yokes to late frame or vice
versa. T.R.S. states this was
due to lack of knowledge of the
effect. See Page 24

Page 24

In any case where a new frame is needed 1 would recommend the early 850 type frame (although the
change-over is a bit complicated for a pre-1971 model with Featherbed-type yokes and adjustable
steering bearings). The steering is more positive at high speed with 850 geometry, but to get the greatest
benefit you also need the 850 yokes (but the 750 type will fit and give the desirable increased trail).

You only really get your head round this by drawing the 2 schemes out on paper and looking at the differences.

kommando · Apr 26, 2018

Notes are here

http://www.billymegawatt.com/uploads/6/8/4/6/6846461/norton_750cc_service_notes.pdf

Yes it does look like some 750,s got the 850 frame and yokes according to the notes.

850 yokes on 750 frame (yet again)

baz

kommando

74ok

delagem

74ok

baz

74ok

74ok

baz

74ok

L.A.B.

Moderator

Danno

kommando

o0norton0o

kommando

L.A.B.

Moderator

74ok

baz

74ok

kommando

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