Hi,

I'm using a readywelder II to weld my exaust pipe, and have core fluxed wire in it. I'm sort of stitching my way allong the exaust, stopping and starting to stop it from burning through.

Will the flux from the wire contaminate the weld? Should I clean back between each weld?

I'm not talking top spec welding here, just good enough that the exaust won't blow or fall apart in the next year or so.

Ta.

You should chip the flux off where you are going to start the weld back up..
What you really need to do is find out why you are blowing through in the first place..Three most common reasons for burning through are too much heat, too slow travel,wrong direction of travel(on sheet metal/ thinwall tubing)..
I am not Familiar with the ready welder II but on my Miller 185 I use the #1 voltage setting and a wire speed between 10 and 15 with .023 wire..I have not welded with the flux core wire so I do not know how it performs compared to regular wire so your settings may need to be slightly higher or lower..
If your problem is too slow travel you are building up too much heat in one area and blowing through and all you can do is move faster to prevent this..
This third one will probably get the arguments started.. Wrong travel direction.. With sheet metal/thinwall tubing(12 guage and smaller) you should push the weld bead instead of dragging it.. Dragging the weld bead is good for getting deeper weld penetration but on the thin stuff you usually end up burning through.. Pushing the bead gives you a wider flatter weld and connects sheetmetal better than than the drag method.. The downside to the push method is your hands are always over the hot bead(so be sure you wear a good pair of welding gloves)..
Another thing to think about is what condition is hte metal you are trying to weld in..If it is almost rusted through then it probably can not be welded..

Thanks!

I'll try the push rather than pull. The metal is in good shape, and i've cleaned it back to shiney with a wire brush.

The ready welder is the portable mig that runs off 2 batteries (Premier power welder sell's em + others)

Ok I had one of those but mine was a Century.. uses the two auto batteries and (if I remember correctly)does not have a way to adjust output voltage the only adjustment on it is for wire speed..

yup, runs of batteries (1, 2 or 3). You can control the wire speed, and that auto-controls the amps as well.

The "pushing" technique sure did help!

Merv---I have used the readywelder and you are going to have your hands full trying to weld thin exhaust type stuff with full size batteries....one trick you might try is to use to very small 12v batteries...like motorcycle batteries...that reduces the amps and lets you turn the wirespeed down quite a bit. Flux core wire is more challenging on exhaust pipe compared to solid wire with gas.....but the stitch method is your ticket.
I tried a single 12 volt battery once but it didn't work for me. Maybe you have better luck...also, maybe a 12v and a 6v would control power better(18 volts).
I didn't clean my re-started flux welds....ever. I was more concerned about the little flux flakes that shot off the weld as it cooled down and my face was nearby. Them things sting.