I know nothing about welding, so say you turn up to a mechanic in a foreign country and you don't speak the language. And using the universal sign language of 'this thing fell off my bike please weld it back on' you manage to get the mechanic to bring out his welder. What do you look out for to make sure the person welding doesn't leave your bike in worse condition than when you arrived?

Always disconnect the earth wire from the battery and make sure that they don't set fire to it, apart from that there is not much you can do. I have been in this situation a couple of times in Mexico and South America and I have limited Spanish but it is pretty obvious what need doing and they generally know what they are doing.

Remove the battery.
Unplug or remove any ECU's within 1m of the weld spot.
If you can remove the part to be welded from the bike, do it.
Get any fuel pipes or bits of loom well out of the way or protected.
Clean off any oil or fuel
Watch your bloke do his prep. It should be a lot of wire brushing and angle grinding not just turning the set up to 11 to blow through the paint.

My favourite return ever was a Landrover ABS ECU with a burn mark either side. The marks matched a welding set earth clamp we held up to it. Needless to say the warranty claim was rejected.

Andy

As others have said not setting fire to the bike or burning out the electrics is a good start but you might want to consider the effect of all those sparks on the cosmetics. It's not hard to get 'overspark' where molten metal sparks fly off and burn through paintwork / fuse with glass etc. Make sure stuff is covered if it's within spark range. Some welders will think of this, some won't.

When it comes to the actual repair, if it's just a steel bracket or something simple that's broken it shouldn't be too hard for a welder to fix but you might want to consider why it broke, and whether it really needs reinforcement. Push the ends together and weld around the crack may not be the best way to do it.

If you need to get something made from scratch welders that spend their day fixing bicycle frames at the side of the road (for example) may not have much of a grasp of materials science. I had to get a replacement kickstart fabricated in Mauritania and the welder made part of it from cast iron - something that's almost impossible to weld successfully. It kept snapping (and being rewelded) until (a week later) I rummaged through a welders workshop in Senegal, found some mild steel bar and had him use that.

If it's anything other than straightforward steel that breaks then good luck. You might find someone who can do stainless but any sort of alluminium alloy is going to need a specialist.

Lastly, don't assume that welding is the only way. You can 'splint' broken brackets and epoxy can often fix holes in castings. I've rejoined many parts with repair plates - drill a series of small holes on both sides of the break and screw a brace across them. When my kickstart was broken between welders I paid the local kids to bump start me. Actually, when the temperature went over 30C, that was better than having the kicker.

Remove fuel tank
Disconnect battery.
Unplug ECU.

The Earth clamp should be as near as the welded joint as possible (Electricity will always take the easiest route).

Welded area needs to be stripped of paint, oil, grease etc. THOROUGHLY. You can burn it off but they'd need some intense heat which you don't want near your bike.

ALWAYS remove the part that needs repair if possible and take that to a welder. Most welders are NOT mechanics. Many mechanics can weld. Not all very well.

Steel is easier to weld. Aluminium needs specialist equipment/knowledge.

If the welder brings out an old Arc unit (basically a stick electrode in a clamp), then he's probably not a welder and just someone who'll have a go.

I'm a mechanic. I also went to college and got my welding qualifications. I weld a lot and take it seriously. But I'm still not the guy you'd call if you want a frame building from scratch etc. It's a professional trade and good work comes at a good price.

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Did some trips.
Rode some bikes.
Fix them for a living.
Can't say anymore.

Depending on which component you weld, removing the tank, etc, seems a bit excessive to me - when every part of the bike where you don't want splatter can so easily be covered up. The major concern would be heat transfer when welding close to anything combustible. When welding, the metal will get scorching hot quite some distance away from the weld. Removing the battery and disconnecting the ECU is good advice.

I second removing the part to be welded - when possible. I also second getting a professional welder to do the welding and the mechanic to do the wrenching, and not vice versa. Often though, you might not have much to choose from other than some local self thaugt mechanic or farmer with a low end hobbyist stick welder.

One idea is to get whomever is to weld for you to weld a test piece of similar metal, thickness, shape and type of weld (i.e. butt weld). Afterwards, inspect the weld - cutting it open if you have to (google pictures for good and bad welds). A farmer may weld beefy stuff all the time, but very seldom thin metal or aluminum.

I only have a little experience with welding. When I had to replace the rear traverse on my series Land Rover (vital to safety that this gets done right) - I didn't feel confident enough to do this myself. I got a Land Rover mechanic and restorer recommended to me. I took it on good faith that he knew what he was doing, and didn't follow my own advice - after all, he had done this exact same job several times before. The top side of the weld looked ok, but I couldn't inspect penetration, etc. First time the car was jacked up, it broke clean off. Luckily the car was still under restoration, and not on the road - otherwise something really terrible could have happened. Truth is, I would with my own limited experience have done a much better job - I would have practiced on a similar piece and kept inspecting the welds until I had it all calibrated (and over engineered), and probably spend more time cleaning up the weld than would otherwise be necessary if a pro did it.

Learning how to weld to a satisfactory level, to cover most of a bikers needs (with an ok result), isn't all that difficult (i.e. welding pieces of metal tubing, angle irons and pieces of sheet metal of similar thickness together (i.e. a broken sidestand or luggage frame. But, don't expect your experience to transfer well to someone else's equipment without having to practice on it. Also, don't expect to be able to successfully weld aluminum, engine blocks, or other difficult pieces - like a thick stress/load bearing piece to a thin piece.

Welding is fun and quite a useful skillet to have as a DIY'er. It also teaches you to be a competent buyer if welding services. You can do a lot with a cheap second hand shit brand mig/mag - even with a much cheaper stick welder. You can get good results with low end equipment, but not without a lot of hickups.

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I used to work as a welder's mate on civil engineering projects, arc welding was used quite a bit at the time for structural stuff that had to hold long term. One of my neighbours is a retired welder who has repaired stuff for me using his arc welder and it's always been top quality. The Ecuadorian guy my friend hired to do a load of metalwork around his house turned up on a bicycle with an arc welder and an angle grinder and managed to make an absolute art out of it using only old scrap metal.

In summary, I have doubts about your prognosis - especially in places where having a MiG and CO2 bottles isn't practical.

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FreeBSD fan since before it was cool ...

I see your point. But it's not what I meant.

There is nothing wrong with Arc welding. Out in the field there is seldom another option. It's still a professional approach in the right environment with the right person behind the torch.

However if you take a welding job to someone who only has a £50 arc welder gathering dust in the back of their shop, it's a pretty safe assumption that they do not take their welding seriously.

Anyone who welds with any regularity or does it as part of their trade will have invested in decent equipment.

__________________
Did some trips.
Rode some bikes.
Fix them for a living.
Can't say anymore.

From what I have seen with the hack arc welding jobs here I think I would pass Ma & Pa shops nothing ever gets fixed you have to fix it again' unless you are in a industrial part of town that does work for the petroleum industry You get what you pay for
In the developing world the service is to please you and get you on your way
If there is no tig wouldn't gas be better Just make sure they dont use a coat hanger for filler
Hell gas welding was used to make every Tubular metal engine mounts and landing gear supports for aircraft up until 1942, Tig was patented after 42
The exception is a good exhaust shops that deals with stainless they will have tig
I dont think arc is is the way on anything on a motorcycle frame
Sometimes welding is not the answer Improvise for the Better
On a tube you can reinforce with U bolts and flat bar Cable clamps come in various sizes to suit your needs if you can't find decent U Bolts
you can even make gussets and use U bolts Sometimes its better to find a shop that has the know how than to destroy the frame with some shitty arc weld job it will cost more in the end

Sorry, I thought we were talking about on-the-road emergency repairs while out in the "adventure zone" (or Spain, lol)

Meanwhile I would have doubts over someone I don't know doing structural repairs with a TIG because it can look very pretty while having no penetration (whereas with bad MIG welds on steel you can often/usually tell from the outside if it's crap or not).

I'm a big fan of proper gas welding, when that's an option (becoming more and more rare in Europe, I don't know what the availability is like in more exotic places).

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FreeBSD fan since before it was cool ...

Something to be aware of is the ground clamp location. It should be as close to the weld as possible, yes, but under no circumstances should the current path go through a rolling element bearing. Welding current traveling through the bearing contact points will ruin the bearing.

Splines on your countershaft expired and you need the sprocket to be welded on as an emergency fix? Don't let the welder clamp onto the engine or frame.

I can't imagine anywhere on a bike where the current will pass through a bearing contact point with it's shell instead the path of least resistance which will be the casing that holds the bearing. Unless the ground clamp is insulated with a paint or coating. An interesting thought though. I suppose anything is possible.

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Did some trips.
Rode some bikes.
Fix them for a living.
Can't say anymore.

Surely the example given is possible Ted? Contact either through the countershaft bearing, or various gear teeth or splines?
Or broken bracketry holding a headlamp and the guy holding the hot stick puts the clamp on the main frame. Current could pass through yoke bearings or even try to pass up the clutch cable in extremis.

I'm not a coded professional, but I just can't see it happening in the real world. Nor have I heard of it. But I suppose it is possible. It would have to be the only current path though. Which is perhaps almost impossible as every bearing is in a casing of some type.

You're dead right though. Always clamp your earth as close to the workpiece as possible. And disconnect the battery.

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Did some trips.
Rode some bikes.
Fix them for a living.
Can't say anymore.

It's called excessive current erosion and is well-documented in the bearing industry as a cause of premature failure.


https://evolution.skf.com/en/prevent...n-in-bearings/

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