Expanding stock tank with hot water and air??

Has any one used hot water and a Little air pressure to expand their stock gas tanks??? I am not to happy with the size of my IMS 3.1 tank on my 06 YZ. I am going to give this a try this week and thought I would get some opinions from people if they have tried it. I plan on bolting on the stock tank and shrouds, closing the petcock, disconnected the fuel line and pouring almost boiling water in the tank. I have rigged up a line that will feed air pressure in to the tank through the cap vent. I am thinking I will sit on the bike and hold my legs against the tank/shrouds to make sure it doesn't expand at that point. Add air and hold it until the water cools. I am hoping to get a minimum of 2.1-2.2 gallons out of it. 2.3-2.4 would be my dream goal but I don't think I will get that. I will post what happens and what size I get it to.

Wish me luck......... (boiling water and compressed air between my legs man I'm sweatin already!!! I better get a better funnel!!!


:thumbsup: sounds interesting to me :thumbsup:

hmm... never heard of that, but it just might work.

sounds a little crazy, but good luck. And post pics of the end result.

I really think you should take video of the process. Depending on the outcome, could be fairly entertaining! :thumbsup:

I really think you should take video of the process. Depending on the outcome, could be fairly entertaining! :thumbsup:

And don't forget a video of the first ride after the "mod" is done... I think a moving fireball would be very entertaining. :thumbsup:

I have heard of the factory teams doing this. Worst case I am out the stock tank which I would not use any way since I only ride woods/harescrambles. 1.8 gallons is just not enough. I need at least 2 full gallons for most of the courses that we race.

No one has heard of any one doing this???

ovvrdrive, That is why I am only thinking I will get 2.1-2.2 gallons. I am sure you could blow it up as fat as you want but I wouldn't want to get the tank walls to thin!! That way I am not a fireball!!!


I really think you should take video of the process. Depending on the outcome, could be fairly entertaining! :thumbsup:

Agreed...I am definitely interested to see if this works. I just might do it myself if things go well for ya.

yeah good luck. Looking forward to your report..

I do remember the factory teams doing that years ago. I think it did get them a little more capacity. Before they shortened the moto length of the GP's (or Nationals) there were some models that didn't have quite enough fuel capacity to make a complete moto. Must have been right after the end of the works bikes, when the production rule came in if I remember right. If I hadn't thrown out all my old MX Actions, Dirtbike and Dirtrider mags I probably could have found something about it in them.

ive never actually done it, but i know you need to use almost boiling water for it to work.

Dirt Bike Magazine recommended it years ago. They even had an article on how it was done. I remember them tapping a stock gas cap for a schrader valve, using boiling water, and air pressure. Its been too many years to remember just how much.

Yeah, get a video....I'd love to see scalding hot water blow up in your crotch! Better have someone standing by with a bucket of cold water if she blows!

My only fear would be the thin wall areas of the tank that are caused by the blow molding process. Good luck, and you may want to put a leather coat between your feature kids and that tank! Post pics!

I am waiting on a petcock for the stock tank. I will give it a go as soon as it gets here. I want to keep my IMS tank intacked in case this does not work. It should be in by tomorrow. I rigged up a hose with a shrader valve that fits to the vent on the stock cap. I plan on pouring in boiling water right off the stove, let it sit for about 1-2 minutes and then pour it out. I am going to have another pot of water boiling ready and fill it right back up. I am only going to fill it 3/4 of the way up. I inspected the areas that I want to expand and I don't want the top part of the tank to move at all. Let it sit for about 1 minute and give it some air!!!!! I know this will work it will be a balance of getting it to expand at the points I want and not have it push the shrouds out. I will take the risk of sitting on the bike with scalding water between my legs :thumbsup: so that it does not push out the shrouds. I really think I can get around 2.2 gallons after mounting the stock tank and looking at were it will expand!!! I have my wife commited to help so I will have her ready with the ice packs and the phone ready to call the ambulance!! :thumbsup: I really think this will not be that bad!!

I will let you know what happens as soon as I get the petcock.


After it blows up in your crotch, you need to get a sound recording of your wife explaining just how you got burned like you did. BTW I wish you good luck.

I just thought that it might help to loosen or take the bolts out on the mounts or it could possbly crack it and weaken it. If your going to squeeze the sides so they don't expand then where else could it expand except upwards but I've noticed on my tank that the plastic on top is very thick so I'm not sure how your gonna do that.

Best of luck to you (and your vitals)

so what happened?

I believe I would leave the tank firmly bolted in place. If not, haw can you controll the mount position. The tank might expand in such a way that it does not fit.

The leather between your crotch and the tank is a really good idea.

Also leaving it bolted up is a good idea. So it still fits.

I would also try to use as much water in the tank as possible, so theres less air (air compresses, water doesn't) more air means more explosion when or if it breaks....if you have more water, less air, when it breaks it'll probably just leak and spray rather than blow up in your face and scald you.

Just trying to play the devil's advocate here, want it to be safe so you can post us the results without a lot of bandages and guaze on your hands. Good luck!

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