Barchettaman

I have a bit of play at the main hinge just above the headset top race.

Before I start messing around with adjustments can any of you give me advice?

The play at the moment feels like a loose headset.

Here are some photos of the locking hinge on my Tern, please say if you’d like another view.

Barchettaman

I don’t think it’s a Q lock post; it doesn’t seem to have any allen head adjustment screws.

Barchettaman

It’s a Link B7 by the way.

Schwinnsta

Loosen the bolt about a 1/4-inch, then with a wood dowel or block, pound it down. It should be loose at this point. If not, loosen some more and repeat. When it's loose, push it to its lowest position and tighten.

sweeks

My Terns have a different handlepost, but I suspect there are some similarities.
When the handlepost closes, it should feel like it's slightly "snapping" into place if it's a variation on the "over-center" type of latch.
If so, wiggle the handlepost with one hand while feeling with the other at the base of the handlepost where it meets the head tube. If you detect lateral motion here, it's the headset.
If there's no lateral motion, then do the same thing with the "feeling" hand at the place where the handlepost hinges. If the motion is found there, I have no advice to give.
The handlepost base appears to have two parallel hex bolts in opposite directions across a gap that looks like steerer clamp bolts. The central (axial) bolt looks like the sort of thing that would be used to tighten a headset. If the headset is loose, obviously there must be instructions somewhere describing the necessary adjustments, but it wouldn't be surprising that the steerer clamp bolts would have to be loosened, then the top cap bolt tightened to eliminate the freeplay in the headset before re-tightening the clamp bolts.
Hopefully this "arm-chair" analysis is close to correct.
EDIT: Nice images!

Duragrouch

If it's a bi-fold frame, any looseness in the stem lower hinge, the headset adjustment, and the frame hinge, can all feel the same; With the front brake applied and rocking the bike fore and aft, feel a slight clunking. Process of elimination:

Assuming the frame hinge is the standard kind with an over-center clamp that holds it closed, make sure it takes some effort to close it, I think perhaps 15mm of gap when the lever first starts to have force; On mine, I need closure to be hard enough that a bit difficult to open the lever to not have any looseness when I push the seatpost and stem in opposite directions and reverse. Note, above does not apply to "clamping" style hinge closures like on some of the pricer Dahons, not sure about Terns.

Next, check the stem latch the same way, if and only if, it is also an over-center style clamp, but I think it is not, I think yours has a wedge-latch closure, in which case you need to check procedure for adjusting.

Then check that the headset adjustment is good; On Dahons, that involved opening the stem latch and partly folding the stem down, loosen the side clamping bolt on the stem base, check slack on center large (10mm) bolt that adjusts headset, this should be just snug, like tightening it with the short end of the allen wrench as a handle, don't reef on it hard. Then bring handlebar stem up and latch, check that handlebars are aligned with front wheel, tighten clamp bolt at base of stem.

Barchettaman

Many thanks all.

there’s no play in the headset; it’s definitely the hinge that isn’t clamping down hard enough. The ‘feel’ of it is just like a loose headset. Sorry for any confusion.

there just doesn’t seem to be any way to increase the clamping force for this design. It’s a bit confusing. With a tighter clamp it’d be fine.

Hmm.

Barchettaman

I think I have located the problem and I don’t think there is anything I can do about it.

The handlebar post clamp area has worn down, there isn’t enough material for the clamp to grip onto, so it can’t ‘bite down’ with any real clamping force.

I think I need a new handlebar post; at least the bottom section.

Barchettaman

These photos show the worn ‘lip’ on the clamping area. The silver clamp is steel I think and harder than the aluminium post so it has worn it.


Worn area circled.

The steel clamp wears the area down.

Up and down play.

Schwinnsta

What is the set (grub) screw in the top of the latch for? Just wondering. It looks like it is crying for some oil.

Barchettaman

I will have look at it now.

Barchettaman

I got a 3mm allen into it but it wouldn’t budge.

Schwinnsta

Can you tell what is it for?

Barchettaman

Not a clue! I fear that the post is toast.

Duragrouch

Rusty screw: Yeah, my thoughts exactly, that may adjust folding tension. Put some quality penetrating oil on it for a few days, like Break Free. Also, look on the rest of the linkage for any sign of of adjustment, like a slot instead of a hole at one of the linkage pivots or attachment. Also, if you don't have, look up User Manual online, it may have details for adjusting the hinge (in link below, User Manual, and also Folding Instructions):

https://www.ternbicycles.com/us/bike...rt/961/manuals

EDIT: Hard to see, but I may see a slot behind the head of the phillips screws on the side.

Duragrouch

IF that screw adjusts latch tension (still to be determined), you may be able to get just that part of the latch from Tern or a Tern dealer.

If you get the screw out, I suggest replacing with a stainless steel, same threads, but socket (allen) head cap screw, so a larger allen size, if the cap will fit under the outside folding lever.

EDIT: For now, to get you going, take an empty soda or beer aluminum can, the sides cut easily with scissors, cut out several layers of "shim" to tape to the inside corner of the hook to tighten things up for now. Or perhaps wrap some copper wire around there.