I finally got around to Boeshielding the interior of my Moto Grand Record's tubes, and when it came time to flip the fork and move the goop around, I noticed what I think is a distressing absence of brazing material on the underside of the non-drive side fork crown. Can this be repaired easily? Is it necessary to fix? (My gut tells me yes.)

First, a couple of overall shots, no obvious damage, no rust. Problem side is the non-drive side, stage right:





DS, which seems fine


DS, detail


NDS, problem side


NDS, detail

From the first pic the DS blade looks like its leaning more outward.

Those cracks under the fork crown and the not-too-clean braze between the blade and the crown look like a fracture waiting to happen. I'd have it inspected by a frame builder to find out if it is safe, and if not, if it is repairable.

I can't say that I've ever looked under my forks. Now you've got me thinking maybe I should.

I don't see much in photos #3 & #4 (NDS) other than cheap workmanship. The filler probably doesn't need to exceed the length of the lug/crown.

Photos #5 & #6 (DS) do look a bit disturbing as if there has been some movement in the fork blade.

As [MENTION=391445]malcala622[/MENTION] mentioned, perhaps you could feel if the fork blade feels loose, or check the fork alignment (quality C&V bike shop?)

I'd probably start looking for a new fork. However, you might have the thread moved to the Framebuilders subforum for suggestions. It might be able to be re-brazed, but you'd have to get the joint very clean, and assuming that is chrome and not paint, a lot of people won't want to work with chrome although technically one should be able to do the work without destroying the chrome (lots of good flux).

Typical French workmanship, I say. It's hard to tell how deep that gap in the braze is. Can you give a measurement? If it's only a mm or two, I wouldn't worry. On that last picture I'd try and gouge out as much of the rusty looking stuff as possible to see how deep the lack of brazing material is. It could be just flux that was never removed. If so, a soak in hot water and some poking around would remove it.

BTW, the only cracks I see are in the paint.

I don't think what you're seeing are cracks, but the brazing is definitely a problem. The casting of the fork crown does not look like the cleanest, so the underside has some craggy "extra" material on either side of the steerer tube's underbelly.

Yes, point taken -- at a minimum, it seems I need an expert opinion from someone who can get his/her hands on it.

Kind of looks like it was rebrazed fron original/like a fill in? Looks too sloppy to me to be original. Compared to raleighs, most motos I had were cleaner.....and that braze looks newer. Of course I can and have been wrong.

Hmm, I will measure later today. I think I see actual space between the crown and the blade, though, so I'm not too confident.

Besides Bernie Mikkelsen, does anyone know of a reputable frame builder here in the Bay Area who could assess this and perform the fix if necessary? He's the only one I know of, but I've never had to research this sort of thing.

Ed Litton in Richmond. Paul Sadoff at Rock Lobster in Santa Cruz. Steve Rex in Sacramento.

Thank you! I had heard of Ed Litton, but he did not come to mind immediately, and the other two are new to me.

I really appreciate everyone's advice.

I like that blog Restoring Vintage Bicycles from the Hand Built Era, and seeing what I saw brought this post to mind (though I did not intentionally steal her turn of phrase):

https://restoringvintagebicycles.com...fork-failures/

I hadn't read through the comments from this post before, and she makes a compelling case for simply getting a new fork. If it's cost prohibitive to fix, I'll look into that option. Since this is a keeper bike, I am not factoring a full quality repaint into the repair cost. I might instead primer it until I can powder coat. Woe is the tinkerer who finds a task beyond his skills...

There is no movement with the blade, and it is not chrome, so at least there is that.

Good point about moving this forum to Frame Builders, though.

Moderators, may I ask that this thread be moved to the Frame Builders forum?

Just click on the red dot, and they move threads quickly.

Done, thanks!

Moderator's response: We don't see why this one should be in framebuilding, sorry.

Framebuilder's response: I wouldn't ride it and there is no way I would spend money fixing it. Really hard to add filler to a rusty gap in an old fork. If you really want to know if there is a problem, get that area sandblasted. I used to keep myself in beer money back in the '70s fixing improperly brazed French bikes, so my guess is it was made after lunch. I wouldn't have touched this one though.

I wouldn't expect movement with a partially brazed fork blade. At least not until the fatigue crack moves through the good filler. It might never happen, it might happen the next time it's ridden, you never know.

I think after a bit of cleaning with an exacto knife, I'm encouraged. (Working from home today, so snuck out to the garage for a minute.) Also, when I posted this late last night, I was a little turned around, and it's actually the NDS that is in question, so I edited my initial post to reflect this.

Here is a better view of the spot, after cleaning out the gunk. It looks like there is indeed a small gap in the brazing material, not that the gap goes the entire length of the lug/blade interface. The brazing material tapers in on either end of this small gap, so it does not look like a break -- it looks to have been painted that way. There is no rust. Maybe not the best workmanship, but it looks like what I thought was gap was mostly gunk. Am I off base, or is my improved mood justified?

Ahhh,

Thanks for the update.

That looks a lot less cracked, and more like an original manufacturing flaw. In which case, if it isn't causing a problem (and hasn't disintegrated in the last 30 or 40 years), then you should be able to ignore it.



Other than that gap in the middle, can a razor blade slide between the filler and the fork blade closer to the edges of the crown?

No, aside from the small gap, there is no other space where a razor blade can fit. I think I'm confident ignoring it, and just being mindful of any change in ride characteristics.

And 't'were mine, I'd put a little acrylic sealant ("bathroom caulk") into the hole to keep spray from going into the fork crown; actually I'd worry more about corrosion of the top of the fork blade, since it's much thinner. But I wouldn't hesitate to ride that fork.

Those fork crowns are folded up and welded on the bottom. You can see the weld on the bottom going across. That braze gap you see on that last picture is probably from a lack of contact from the filler material on the weld seam. That's common on old Motos and other bikes that use a stamped and welded fork crown.

"this is the end, my trusted friend"

​​​​​​​At this point I would just be thinking about the integrity all the time, maybe even for years, but "this is it, time to go...'

I looked at three of my Motobecanes.

Mirage. Pressed steel and welded crown, much like the OP. No "gap" like the OP has, but the filler is perhaps 1/2mm shy of filling the space between the crown and the blade to the top.
'
Grand Touring. Appears to be a cast crown. There is a big lump of weld or braze on the inside of the fork blade, but nothing too odd.

Grand Jubilee, also cast. Has a fender, and hard to visualize underside. May have a similar lump to what the Grand Touring has.

None of the bikes have fork tangs on the inside.



There were earlier threads about the increased strength from the fork tangs, but a lot of older bikes don't have them.

This thread has been reassuring -- I appreciate everyone's input...