MIG welding frame mods?

Doing some mods and I want to weld in some extra 1" tubing in my frame. Can I use MIG welding? I've done a bit of this fairly well. Or is the MIG method (flux wire welder)considered too weak for a frame mod?

Flux core mig usually lets you do the heaviest welds for a given machine, but you shouldn't need anything that heavy, unless you don't have the gas rig.

The original frame welds look like gas-mig to me, which you usually have to do indoors because outside is usually too windy. If you can do gas MIG indoors, you should be fine. If you are doing gas mig outdoors, pick the calmest day you can.

Flux core will work, but will be more messy. It should be ok if you don't mind doing a lot of clean up afterwards on the welds to make them pretty.

Obviously, whatever you do, practice a bit on some scrap tubing first to make sure it's setup right for the type of connection you are doing. Then cut it apart and check the weld.

Also, should add, this is all assuming you are using the same type of tubing the frame was made of. Some have mentioned using bicycle tubing, which can be harder and thinner. For that you'd probably want tig.

Well, I don't have the gas rig for my welder and unfortunately can't afford one, it's just a little 90 amp flux core wire welder (although I've done some 1/4" stuff with it-not that I trust it). Also, I asked this a number of months ago but forgot to note it: What kind of tubing do these bikes use? I'm guessing DOM of some type. It's an '82 KZ750H3 LTD.

mild steel tubing,or plumbing pipe as some call it! :laugh:

With your welder you should have no problems making a strong weld as long as you're getting enough penetration. The wall thickness is probably no more than 1.20, just make sure you set your machine to match the wall thickness. As usual, with flux core be prepared to chip/brush the slag before you paint. Good luck!

0.100" thick wall, mild steel tubes. Perfect for a mig/flux core. I would prefer proper mig welds for cleanup purposes, but run what you brung. As others have suggested, setup some practice welds, and take a cross section of the weld to check penetration. I second the observation that the factory welds appear to be mig. What mods are you doing to your frame?

It's called (or so called) konging the frame, among other names, but I'm just doing the back part of it. It's where you cut out the top rails running straight back from the rear of the tank to just before the shock mounts. Then you weld rails back in that go from the tank to about 5" down the rear down tubes. This gives the seat area a low hard tail look but retains the shocks.

Ends up looking like this....


Think I actually found this pic here on the site somewhere (sorry to the originator for using it)!

If properly prepped and welded, MIG will be just fine.

I would go ahead and do it with the flux core. How many welds will you have to clean up? Maybe four. Go for it.

Yea, think I will. Looking at it, the stress will be mostly trying to compress the new rails toward their centers, rather then trying to pull the welds apart at the ends. Seems that would aid in strength. No? A last question: I know that flux core mig welding creates a lot of slag. Is there a way to cut down on this?

polkat wrote:

Yea, think I will. Looking at it, the stress will be mostly trying to compress the new rails toward their centers, rather then trying to pull the welds apart at the ends. Seems that would aid in strength. No? A last question: I know that flux core mig welding creates a lot of slag. Is there a way to cut down on this?

Yes, clean, clean and clean the metal before welding. Get a steel brush that you only use on mostly clean steel so it won't have contaminants. Also if you use sandpaper, use only fresh sandpaper or grinding wheels that haven't been used on anything else. Always finish with the steel brush so there won't be any aluminum oxide on the metal.

Also practice on similar tubing to dial in the feed and amperage really well so you can get a good weld with minimal wire useage. The more wire you use, the more blobs will be created with more slag.

Almost forgot, with flux core, if you have to stop in the middle of a bead, and it's in a critical area, clean off the scorch marks from the unwelded portion or it will be hard to continue the bead.

Laziness ends up being messier and if you want to make it look nice, will end being more work in the long run.

Common sense, but don't rush. I always have to remind myself of that.