Any suggestions on how to repair/weld this? (lawnmower gas tank)

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After noticing for a while that my lawnmower was hard on gas, I realized that part of the top of the gas tank was broken off.The lawnmower is as old as me so it's an all metal model (not the crappy plastic things they sell nowadays) that spins so fast I could probably chop the 1/4" corner pin on my lawn without bending the crank.  I'd rather fix it than get a new one.Not wanting to weld a gas tank (I've heard horror stories), I chopped the top off with a hacksaw so I could keep the filler neck and carb plate.My plan was to fabricate a tank but weld the top portion back onto it.  The top looks like cast aluminum (doesn't stick to a magnet and left a whitish powder on the table after cutting it) but I can't positively identify the metal being new at this.Has anyone here ever done this?  Any suggestions?  Am I wasting my time, should I just buy a new mower?Thanks in advance for any advice.
Reply:buy a new one would more of a pain to try to repairget a used one ---or buy a new mower
Reply:Before it was cut in pieces  I would have just covered the hole with a fibreglass patch filled with JB weld or epoxy filler.Now looks like a problem esp because of the way the tank bolts to the carb??? or intake???Suppose one could mill up a new top to match and weld a new tank up, but why on an old lawnmower that is likely more than half worn out anyway?
Reply:I see these all the time on junkers.  I bet you can get a near perfect one if you look around.  I pick up old junk pushmowers all the time and the tanks are always in good shape.Smithboy...if it ain't broke, you ain't tryin'.
Reply:That top piece is a zinc die casting, not aluminum. I think the suggestion about getting a 'new' tank from an old engine is probably the easiest.What make and model is the engine? It should have the model numbers stamped somewhere on it if it's a common brand like B&S or Tecunseh.The epoxy patch idea would have been the easiest in the beginning!
Reply:It would be hard to find parts up there in the north, they hardly got lawns. But with the internet seems just about anything can be found.
Reply:The patch wouldn't have worked because there is a mount that bolt to the engine right where the hole is.  The vibrations would have torn the patch to pieces (probably what broke the gas tank in the first place).Anyway, thanks for the advice guys but I just bought a new lawnmower.
Reply:Originally Posted by TimberwolfIt would be hard to find parts up there in the north, they hardly got lawns. But with the internet seems just about anything can be found.
Reply:"Not wanting to weld a gas tank (I've heard horror stories) "what, were you afraid of that puny little tank with seveeral large holes? Very easy to rinse that out.????LOL  you done screwed that up big time.   how about asking for reccomendations BEFORE you hack apart the next "project"
Reply:Originally Posted by dsergison"Not wanting to weld a gas tank (I've heard horror stories) "what, were you afraid of that puny little tank with seveeral large holes? Very easy to rinse that out.????LOL  you done screwed that up big time.   how about asking for reccomendations BEFORE you hack apart the next "project"
Reply:help?   who said I help?   it's far too late for help.   that was humor.  really,  -by your own statement: "Anyway, thanks for the advice guys but I just bought a new lawnmower"     so, allready your problem was solved.I didn't mean to be offensive.  just a little good natured ribbing.  my appology that it didnt convey as such.
Reply:Haha, no offense taken.  I'm new to this whole thing so I learn as I go and of course, screwing up every now and then is part of the learning.Lurking and occasionally posting on this forum has taught me a lot.
Reply:Originally Posted by x1riderNot wanting to weld a gas tank (I've heard horror stories), .
Reply:Gas tanks are easy to weld on if properly prepped. You need to rinse, wash, repeatedly some times, then air and dry out the tank. It can be a lot of work and time and you need to let it sit for awhile to dry it out properly. The only time I have heard of one blowing up is when someone didn't take the time and got in a rush. The tank would have be an easy fix had you let us know before you cut it apart. Sorry for saying though.I would look for a good used tank or if your heart is really set on it now. try to shape some sheet metal and build a new one. Make sure all the joints are welded very well as vibration failure is very high on sheet metal in those applications.Good luckMiller DVI2Lincoln Precision Tig 225Thermodynamics Cutmaster 38Everything else needed.
Reply:About tanks blowing up, the thing that scared me the most is that my own secretary's husband, who is a welder for a sawmill, suffered 3rd degree burns after trying to weld the mill's owner's gas tank (needless to say the thing blew up right in his face).  ...and he's an experienced welder!A few people told me about the fiberglass fix, but my concern was the mount that bolted to the engine.  I don't think the fiberglass would have survived the vibrations.Someone earlier mentioned that the metal was a zinc die casting, can you even weld that?  (my welder is a Miller Synchrowave 200).Thanks again for the input.
Reply:In cases just rinsing is not enough. Where tanks are coated on the inside or have potential residues the heat from welding can off-gas enough volitiles forming fuel for a potential exploxive mix in the tank/cylinder.I have filled tanks compleatly with water or purged with continious exhaust from a car engine to keep the O2 low enough to avoid having an expolsive air fuel mix inside while welding or cutting them.
Reply:car gas tanks = big volume (15+ gallon) with relatove tiny spout ( 2sq") holes.= no big deal here
Reply:Agree, the lawnmower tank is too small a space and too much exit area to detonate. But I was very careful let me tell you when I made a water jacket wood stove out of scrap 100 lb propane tanks.Back to the original problem, I think before it was cut apart it might have been possible to fix the dicast tank by filling the tank with sand to keep the shape, then fill in the hole with eutectic filler rod, durafix or what ever low temp aluminium alloy rod using a propane torch. chunk of stainess rod to help push the puddle around. Not likely pretty, but might have plugged up the hole. What you guys think?
Reply:In the early days of die casting zinc alloys, lots of things like Magnetos were made of the stuff. Over the years, lots of them have fallen apart/swelled/broken due to inter-granular corrosion and other problems. Some of the alloys just weren't stable over time. Zinc has  fairly low melting and boiling temperatures too. These both make true welding of the metal more difficult, especially with an electric arc. There are some soldering alloys (one of which I once saw 'demonstrated' during a TV 'infomercial' !!! ) which I think contain lots of cadmium, that can be used successfully for clean metal but metal whose pores contain gasoline is not as easy to fix and the result won't be as good as the original piece. Finding a replacement tank should be much easier. Or a new lawnmower.
Reply:Rinse, clean and purge with argon. No explosion. Expensive? Yes. Safe? Yes. You have remaining fuel and supply the heat but where is the O2? Remove any three and no boom.