Welding thin stainless tubing

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I have a question about welding thin walled (22 gauge) stainless tubing. I am trying to build a new header for my motorcycle. I built one in the past, but my welds looked really bad. I have progressed a lot since then, but I have hit a stumbling block.When I fuse two peices together, I get nice shiney perfect welds. The second I add filler, my welds turn gray and dull. I'm welding 304 with 308 filler. I think it's 5/32 filler. It's pretty thick for the job and I have a hard time getting it under my torch into the puddle. I'm running straight argon and 20 cf gas flow.My questions....what causes the dull, gray appearance? How do I fix it? When fusing tubing is it important for the weld to penetrate through into the inside? Will back purging eliminate the tendency for the weld to burn through and sag?Here's my current header. The new one will stay inside the frame and come up through the swing arm.On the bike.....
Reply:I've had the exact same problem with adding filler to 22ga sheet, but I am using 308l 1/16 filler.Yes, back purging will help alot, actually it's a must with thin materials. Most of the time I use Solarflux-B. It works well, and is quick and easy. You just mix it and paint it on the backside, no setup. It seems expensive when you buy a can, it's around $40.00 for 1lb, but that can will go a very long way. I've been dipping out of a can for 9 months now and the can still looks full.Nice bike!
Reply:you should be able to just fuse it and it will hold up just fine..5/32 filler?    look at it this way.. the filler is way bigger than the base material.. you need too much heat to melt the filler and then the base material says "screw this its way too hot for me i'm outta here"(well it don't actually say anything but you get my point)1/16 would be more like it..try the fuse method.. ends that are perfectly matched should give good results...if not get thinner wire...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:It is best not to use a filler wire that is thicker than the base metal that you are welding on . In forty years of welding this has worked for  me.
Reply:I have seen grayish welds from people pulling the rod too far from the puddle, and away from the gas. When you "dip" your rod dont pull it out so far or you will be out of the shield gas thats coming out of your cup. One of the most common mistakes I see with stainless. You usually dont have as much of a problem with alum or mild steel, but stainless is different. Try this.... weld once and purposly pull your rod out of the sheild gas, then run another pass and be sure not to pull your filler rod out too far. You'll notice a difference. Not sure if this is your problem but just a shot
Reply:I believe Tigman has a ringer there.  If the tip of your wire gets contaminated, cut if off with some wire cutters.