MIG Welder mini-project

So before I can start looking at fixing up the frame, I need some welding kit. And a minor detail is that I need to teach myself to mig weld! I'm reasonably confident that I'll be able to do that, as I did a bit of gas welding and arc welding many years ago and was OK at that. How hard can it be?!

I picked up my Facebook Marketplace bargain (hopefully) - £20 but with a wire feed that keeps jamming.

It was pretty filthy so the first job was to strip it down, clean all the accumulated crap from inside it and give the outside a good clean up. I also bent a couple of the pieces back into shape so that screw holes etc lined up properly.

Before:

... and After:

I noticed that the earth lead connection to the clip was hanging on by about half its threads, so remade that properly onto the other arm of the earth clamp.

I cleaned the wire feed mechanism up and gave it all a good lubrication. When I plugged it in and tried to feed some wire, it did indeed jam. But the wire feed mechanism appears sound, so I'm assuming the problem is in the liner down to the torch. This is made of plastic and a known failure point. I removed it and ordered a metal liner which apparently is about 20% of the friction of the plastic ones. I also ordered a new shroud and nozzles for the torch.

This picture shows the plastic (black) and wire (white) liners next to each other.

The original shroud and tip looked past their best - these are consumable items, so i replaced those as well.

Still some fine tuning to do, but we have wire being fed!

I tried a weld and it worked - although not the prettiest weld in the world. I definitely need some practice.

So, it's working but I'm not convinced that I've fully got to the bottom of the problem, as the wire speed can be a bit erratic and twice the motor has just not turned, although I can hear the relay clicking. I may investigate replacing the motor if I can find a cheap alternative.

Updated 24/9/23:

I found a replacement feed motor and mechanism on EBay that was only £10 but coming from China. When it turned up it was nothing like the size of the original! It looked like a big version of the sort of thing we had in Hornby trains whereas the original is about 5 times as big and then runs through a worm drive gearbox. Somehow it didn’t look like it would “cut the mustard” 🙄. I did a bit of research later and found out that the original feed motor and gearbox were truck wiper motors!

So I pulled the motor off and stripped it down to see if I could find anything. The brushes had plenty left on them but were a bit sticky so I cleaned and lubed them. Then I gave the commutator(?) ring a good clean up with emery and cleaned everything with contact cleaner. Put it all back together and it all seems a lot happier, so 🤞🤞🤞. 

I also realised that the tip shouldn't be sticking out from the shroud so much as it is, which will stop the gas protecting the weld effectively, so I need to maybe put a lock nut on behind it. I only have some quite thick scrap steel that I’ve been laying down some weld on so I’ll get hold of some thinner stuff now so that I can experiment with settings etc to get things set up ready to take on the frame 😃.

Electrickery

The wiring provided with the bike was a right mess! The original loom had been left intact but then roughly cut into and hacked about to wire into the moto-gadget unit and non-standard switchgear.

I spent a happy hour or so in the shed trying to disentangle and understand the various different circuits. There weren't many block connectors, with most things being hard wired in. As I'm going to completely rewire the bike, I cut the loom down into sub-sections, clearly labelling everything so I knew how to reconstruct it.

I ended up with this rat's nest of redundant wiring, which went straight in the bin.

But more importantly, I also ended up with a clear set of components and a clearer understanding of how to rewire it all using the moto-gadget unit, when the time comes.

I also used a spare battery to check things like the horn and also how the wiring for the repeater lights in the speedo are wired up. Happily, all worked fine.

Some history.

When I bought the bike, the current owner gave me a copy of the previous owner’s registration document. I wrote to him a couple of weeks later to see whether he possibly still had any of the parts left that he’d removed when he modified the bike.

Yesterday, I got a really interesting email from him with some history of the bike. It turns out that he bought it in a pretty sad state, after it had been left to rot at the back of a garage for 17 years. Lots was missing from it and the wiring loom had been nibbled by rodents!

Seeing that condition, I understood why he had done the build in the way he had. Apparently, I have been quite wrong in describing it as a cafe racer - it's a "brat bike" (whatever that is!)

This was the bike when he finished his project:

He thought the mileage before he changed the speedo was around 35k miles. The compression was perfect, which was the deciding reason he rebuilt it. 

He said that it was in perfect running condition, after fitting new carbs from Italy and electronic ignition, and used to run really well.

The thing that I was most pleased about was that he sent me a link to a YouTube video of bike in former incarnation and that did indeed show it running really well, so I am very hopeful that the engine should need little doing to it.