MK3 Seat lock

gregg-k · May 31, 2013

Does anyone happen to have a photo of the area around the MK3's seat lock and right hand side shock gusset plate ... or perhaps point me to one?

Like so many bikes before it, my MK3 arrived as a giant puzzle of pieces; and even though I'm expert on things Norton, the small details have taken silly amounts of time to sort out.

It's now about 99% done, but for the life of me, I can't figure out the order of assembly of the seat lock onto its bracket, and onto the gusset plate on the frame. I've looked at the manuals and searched this site without any luck, and I've tried every way I can think of to assemble the lock and its bracket onto the frame ... no build up I've tried allows the bracket to sit nicely against the shock gusset, with enough space for the jillion spacers, nuts and washers that have to go in the allowed space. I'm beginning to wonder if some "generous" soul threw in a handful of spare bits in the box that contained the lock ...

Anyhow, the only build up that held any promise was with the lock's bracket planted outboard of the shock stud, but that leaves very little thread for the seat knob after the cup washers are fitted. I generally don't ask for help, but the time has come ... while I am still sane enough to understand the answer!

Many thanks,
... Gregg

L.A.B. · May 31, 2013

gregg-k said:
The only build up that held any promise was with the bracket outboard of the shock stud

That does seem to be correct if you meant the shock mounting plate? The stud hexagon is outboard of the lock plate.

gregg-k said:
but that leaves very little thread for the seat knob.

I don't know why that should be? Perhaps the answer is in the photo?

79x100 · May 31, 2013

My lock was missing when purchased but I assembled from new parts and arrived at the same order. It isn't immediately obvious or logical, as I recall.

Having ventured into the garage, beer in hand and not being as quick on the draw as L.A.B., I thought I'd post the photos anyway

It's unbelievable how the digital camera shows up every mark on the enamel...and my grab rail's rusting inside...

jaydee75 · May 31, 2013

I'm a little late, but here's some more. Original since 75 when I bought it.

gregg-k · May 31, 2013

Thank you all so very much for these helpful photos! It appears they consistently show the bracket with the teardrop shaped hole (for the lock) positioned flat against the shock mount gusset plate in the frame. THat was my first guess.

However, when I assembled it that way, there wasn't enough room between the lock bracket and the inner shock gusset plate for the various spacers and hardware.

I'm beginning to wonder whether the inner shock gusset plate is bent, thereby using up some of the space for the lock?

Question: does the large nut (1" across the flats) for the lock go:
- between the plates, so that it holds the lock to the lock bracket,
Or
- does that nut serve to hold the lock assembly complete with its bracket to the inner gusset plate? I think I see it both ways in the photos.

Anyhow, one thing is clear from the photos posted by L.A.B and 79x100: my build up that showed the most promise (ie: with the lock bracket outboard of the right side shock stud is not correct. The shock stud holds the lock bracket tight against the outer shock mounting gusset plate.

With that knowledge, I will begin assembly and look for the anomally(ies) that are preventing the lock from fitting correctly between the bracket and the inner gusset plate.

Many thanks for your collective help!
... Gregg

gregg-k · May 31, 2013

jaydee75 said:
I'm a little late, but here's some more. Original since 75 when I bought it.
<SNIP>

Excellent, jaydee75. Your photos confirm exactly the way I had tried it the first time (but couldn't get it to work). Now, I'm convinced the inner gusset plate must be bent and has not left enough room for the lock assembly.

Many, many thanks, gents!
.. Gregg

79x100 · May 31, 2013

gregg-k said:
Question: does the large nut (1" across the flats) for the lock go:
- between the plates, so that it holds the lock to the lock bracket,
Or
- does that nut serve to hold the lock assembly complete with its bracket to the inner gusset plate? I think I see it both ways in the photos.
. Gregg

They all look to be in the same order to me., although Jaydee has the correct tab washer and mine has a plain one.

Jaydee, when they were new, did seat and ignition have matching numbers ? Despite rummaging through lots of dealer stock, I've never found a pair.

jaydee75 · May 31, 2013

Nope, typical Norton. Mine came with 3 pairs of keys: Ign, Fork lock, and Seat lock.
Jayde

79x100 · May 31, 2013

jaydee75 said:
Nope, typical Norton. Mine came with 3 pairs of keys: Ign, Fork lock, and Seat lock.
Jayde

You can see the three keys hanging on my key ring. I managed to get the numbers pretty close but came to the conclusion that they were in different ranges as I never found an overlap. From what I can remember of my Grandad's old Wolseley, the seat locks were left-over 1950s car door locks.

gregg-k · May 31, 2013

79x100 said:
jaydee75 said:

Nope, typical Norton. Mine came with 3 pairs of keys: Ign, Fork lock, and Seat lock.
Jayde

Click to expand...

You can see the three keys hanging on my key ring. I managed to get the numbers pretty close but came to the conclusion that they were in different ranges as I never found an overlap. From what I can remember of my Grandad's old Wolseley, the seat locks were left-over 1950s car door locks.

True enough: they must have made piles of them, because my old Lotus used the same bolt-in lock on its doors ... you don't have to wonder why I never locked that car ...

.. Gregg

gregg-k · May 31, 2013

Problem solved! - Re: MK3 Seat lock

With thanks to all of you who posted the detailed photos, I zeroed in on what the correct build up should be. I then determined that the gusset plates were slightly bent and causing the lock bracket to misalign.

When one fixes something, it has to be the right thing ... so, why were the brackets bent? The answer lay in the bike's new Hagon shocks.

The bike came with new Hagons, and they were fitted with Metalastik bushes that were too long ... the workshop manual calls for 0.750", and these were 0.950" long. With some quick work in the lathe, I reduced the length to the correct dimension. Careful straightening of the gusset plates with some 0.750 alloy bar stock and 'C' clamps, and they were back to being dead flat and aligned.

With the gussets corrected, the lock assembly went back in just like on jaydee75's bike, wiht the tab washer and large nut on the 'outside'. Case closed (except for correcting the left side shock as well).

Thanks again, gentlemen!
... Gregg

L.A.B. · May 31, 2013

Re: Problem solved! - Re: MK3 Seat lock

gregg-k said:
The bike came with new Hagons, and they were fitted with Metalastik bushes that were too long ... the workshop manual calls for 0.750", and these were 0.950" long.With some quick work in the lathe, I reduced the length to the correct dimension.

Well, the lower bushes should be 0.950" on MkIII shocks.

gregg-k · May 31, 2013

Re: Problem solved! - Re: MK3 Seat lock

L.A.B. said:
gregg-k said:

The bike came with new Hagons, and they were fitted with Metalastik bushes that were too long ... the workshop manual calls for 0.750", and these were 0.950" long.With some quick work in the lathe, I reduced the length to the correct dimension.

Click to expand...

Well, the lower bushes should be 0.950" on MkIII shocks.

Thanks L.A.B, I haven't altered the drive side shock yet, so there's still time.

But, I just re-checked Section F6 my factory manual (wondering how I could have missed that detail), and the only bush dimension given is the 0.750 ... with no mention of a larger dimension at the bottom pivot. Couldn't find anything in the Technical Data section, either.

I can see that the 0.950" bushes would give more clearance at the lower/swing arm pivot point, but the 0.750 bushes clear fine, too.

...Gregg

L.A.B. · May 31, 2013

Re: Problem solved! - Re: MK3 Seat lock

gregg-k said:
But, I just re-checked Section F6 my factory manual (wondering how I could have missed that detail), and the only bush dimension given is the 0.750 ... with no mention of a larger dimension at the bottom pivot. Couldn't find anything in the Technical Data section, either.

I agree, you won't find anything in the manual, but the bush widths are listed in an old Hagon shock catalogue I have.

If the lower bushes are 0.750" wide then the lower ends of the shocks will be pulled inwards when the mountings are tightened so the shocks will end up leaning away from each other.

The Hagons on my MkIII have the correct wider lower bushes but they still required an extra spacer washer placed inboard of each lower shock bush before the shocks were set parallel to each other.

(Note that the need for the wider lower bushes only applies to the 850 MkIII model shocks)

gregg-k · May 31, 2013

Sounds good to me L.A.B ... it's less work too, since I don't have to machine any more bushes. Tonight I'll swap the 0.750 bush I modded from the bottom of the RH shock and move it to the top of the LH shock.

Thank you for clarifying this.
.. Gregg

gregg-k · May 31, 2013

gregg-k said:
Sounds good to me L.A.B ... it's less work too, since I don't have to machine any more bushes. Tonight I'll swap the 0.750 bush I modded from the bottom of the RH shock and move it to the top of the LH shock.

Thank you for clarifying this.
.. Gregg

Done. I now have the modded 0.750" bushes in the top eyes, and the 0.950" bushes at the bottom. Lots of clearance at both ends. My lock even works ...

Cheers!
... Gregg

MK3 Seat lock

gregg-k

L.A.B.

Moderator

79x100

jaydee75

gregg-k

gregg-k

79x100

jaydee75

79x100

gregg-k

gregg-k

L.A.B.

Moderator

gregg-k

L.A.B.

Moderator

gregg-k

gregg-k

Similar threads