Welding Tips and Tricks

This is something I would love to learn how to do, it might be too soon. I'm not that good yet.
I have couple of dents in a 5 gallon motorcycle tank. I've had the inside coated and I've been fighting my hvlp set up to get the moisture out. The week I finished my cooper cooling lines for the compressor I had a run in with murphy's law. I got another big dent in the tank. Oh boy was I pissed. I think there is two options body filler or cut her open and get those suckers out. Now if I open the tank I would also like to move the fuel neck over to the center. I brazed a taller neck on the top side using some exhaust pipe, to install a Monza style.

What would be the best way to open her up, cut the pinch welds, if so I would want to get rid of them too.
I'm such a newbie I don't even know what else to ask. Any tips?

I'm thinking about trying to see if I can find another tank to practice on, off ebay or something.

Not my area of expertise, but could you weld up a heavy arm to reach inside, to work out the dents without cutting the tank open? Either by using it as a hammer, or an anvil/backstop?

Completely OT, but I'm also curious about your compressor cooling lines setup. I just fashioned one myself, but the humidity here is so low that I'd have to be sandblasting before I'd drive enough CFM to see if it really works.

Cheers,
Richard

I've tried the arm thing, I may try again. The thing about it is since there is a long neck from the factory inside the tank and I added to it on the top??? My attempt before failed couldn't ever get any leverage because the long fuel neck and the center ridge for fitting on the frame.

It's probably not perfect but it seems to work. I don't have a very powerful compressor but the biggest and best I've ever owned. 60gal 3.1 hp motor, It's going to big enough. Anyways a rubber hose from compressor travels 1' down in 3' foot distance over the 1/2" copper hard line, then first p trap. I used type L, I read the type M was strong enough. I have never soldered copper lines either. So two ball valves and two elbows later I had 30' of copper tubing. I recommend using the push on fittings. So my lines go side to side starting at the bottom going up in 5' sections. Then come back out the top to another p trap. I plan on adding two more ball valves to each p trap. Then the hard lines go into union then a oil and water separator and desiccant filter then the devilbiss snake desiccant filter.
Long story short. Before this cooling system I was getting dimples in paint all sorts of problems. I painted my triple trees the other day just with epoxy. Came out like glass! It works. Maybe I can post some picks of it later.

In my mind's eye, I pictured an arm fab'd out of like 3/8" steel, attached to the front of an air hammer, with a very blunt head to tap out a dent from the inside. Or maybe mounted in a vise to hammer from outside. But, I'm talking out my rear here because I've never done body work, so... I just know what I'd try before cutting it open.

For my air cooler, I did a 3/4" line out of the tank, no P trap, feeding to an upper manifold. From there, four 1/2" tubes drop about 48" to a lower manifold on a 45-degree slope with a moisture trap. Basically, a radiator made from 1/2" copper. My tank's outlet is only 1/2", but I stepped up to 3/4" immediately. The two design principles were a) lots of surface area to dissipate heat, and b) large pipe capacity to slow down the air velocity so the moisture could condense instead of being carried through the filter. Maybe this fall when the humidity picks up I'll know whether it really works.

Cheers,
Richard

Unless your very competent with sheet metal work I would not cut it apart except as a last resort - tanks are usually very deep pressings done with a very high tonnage creating extreme stresses - the factory weld is a kind of rolling continuous resistance weld that joins the pieces together & does not distort much - anytime you cut something like this it releases some of that stress & changes shape - the more you try & weld it the worse the distortion gets - I would be tempted to use filler if the dent is small - if its big then I would use air pressure & oxy / acetylene though this is going to destroy the internal coating - I have rarely done a tank - but over the years I've had a bunch of 2stroke expansion exhausts off motocross bikes to repair - when they drop the bike on the exhaust side it is the first thing to hit the ground & dents / flattens easily - it's not possible to get inside to push out & the time to cut them apart & beat back into shape is not worth it so I have a kinda redneck solution ! first wash or of choice steam clean the thing internally to remove any combustible residue - now I blank the head flange & make a flexible connection from the tail pipe to a regulator - of choice I use CO2 or nitrogen for safety - but in a pinch you can use air - now pressurize to say 5psi ( initially ) - get an oxy welding torch with a smallish nozzle in & gently warm around the dent - do not get too near the edges - start about 1/3rd of the way in from the edge & heat toward the center of the dent - go gently - as the heat does it's job you will see the dent coming out - the right combination of internal pressure & heat is something you get from experience - if the dent is not moving then up the pressure a little & try again - your unlikely to get it perfect using this method - but I've got expansions so that with a coat of heat resistant matt black paint the repair was not noticeable - on a tank try not to go too much & maybe accept a small skim of filler afterwards - I guess if you go too far it may dress back in - biggest danger is DO NOT OVERHEAT the sheet as the pressure will blow a hole through instantly or make a bubble - this is where the inert gas pressure is infinitely safer than air.

Best of luck however you tackle it.

Fill tank with water, put cap on, put in freezer.

Have you guys seen paintless dent repair (PDR) on motorcycle tanks? Depends on where you live of course. I live in Vegas, nearest competent PDR folks are in Los Angeles.

check out: tjOjYvT0jEU

And the bad news.. how do I know this? I dropped a 2x4 on the wifey's tank while doing some woodworking. SV1000s. Ouch. I've spent a lot of time around the PDR process, and a motorcycle tank repair is not for a PDR rookie.