Scooterotica

I would like to pressure test an Asian long range tank before i fit it but was wondering if this is something I could do? If so how would you go about it or is it somthing best left to the pros?

If so where do you get somthing like this done, obviosly i want to know if it leaks and if so where from?.....

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Sef

I'd seal the filler cap off and make some sort of adapter with a tyre valve which can then be gently pressurised with a tyre inflator.

grayspeed wrote:I'd seal the filler cap off and make some sort of adapter with a tyre valve which can then be gently pressurised with a tyre inflator.

I thought along the same lines, presumably you could then put it in the bath and look for bubbles ala my chopper way back when. I kind of like the the idea of doing it like this, seems very heath robinson....

You would not need to go to those lengths. You could fit a petrol tap turned to the off position and half fill the tank with parafin. Dry the outside of the tank well and progressively turn the tank over so successive seams ar under the level of the parafin. Check for leaks/wet spots on the outside, parafin will find a way through. The petrol cap needs to have a breathing hole for this.

Second option, if you don't like parafin is block off the tap hole in the same way and use a petrol cap with blocked breather This could be done temporty with some insulation tape. Fill the tank carfully with hot soapy water then give it a little shake and roll around. The hot water heats and expands the air in the tank and will blow bubble out of any leak holes.

This is a gentle way of adding some positive pressure in the tank. Personally, I would not like to put in valves and pressurise with pumps or air lines. It is asking for trouble and will prbably end up like Mr Chinery & that tortoise in the League of Gentlemen.

If your tank has a fairly standard filler cap, you can do it this way.

Fit a fuel tap and turn it off. Now cut the valve out of an old inner tube, leaving about an inch and a half radius of rubber around the valve. Place this over the filler cap neck and secure it with a jubilee clip. Pump up the tank using a foot pump (about 8 or 10 pumps should be plenty).

Now mix up a solution of water and washing-up liquid (like a kid's bubble mixture) and apply this to the welds on the tank using a small paint brush. If there is a problem, there will be bubbles (both large and small).

I have used this techique many, many times on cut-n-shut tanks I have made. It works. The main advantage over the paraffin method is that you can then re-weld the seam without fear of a lethal explosion. You also haven't introduced any water into the tank, so it won't rust.

Our testing Jig isn't too far removed from Martins

Knowledge wrote:If your tank has a fairly standard filler cap, you can do it this way.

Fit a fuel tap and turn it off. Now cut the valve out of an old inner tube, leaving about an inch and a half radius of rubber around the valve. Place this over the filler cap neck and secure it with a jubilee clip. Pump up the tank using a foot pump (about 8 or 10 pumps should be plenty).

Now mix up a solution of water and washing-up liquid (like a kid's bubble mixture) and apply this to the welds on the tank using a small paint brush. If there is a problem, there will be bubbles (both large and small).

I have used this techique many, many times on cut-n-shut tanks I have made. It works. The main advantage over the paraffin method is that you can then re-weld the seam without fear of a lethal explosion. You also haven't introduced any water into the tank, so it won't rust.

This sound like the go and have most of the things i need. If you do find a leak in the seam on the side that shows how do you go about welding it without just lobbing a load of metal on the outside of the seam making it ugly?

Thanks

After you find a leak with the parafin method you wash out with hot soapy water. This will not lead to rust as once you have inspected / repaired your tank you wash out with a solvent or similar to jizzer / parafin or whatever. Lots of washing is a good thing, great for removing blasting debris etc, provided you give it a final wash with something other than water, jizzer is pretty good stuff and has a rust inhibitor too.

Personally, if it is an original tank i would petseal it (good for pin holes and small leaks), don't bother trying to weld. Worst case would be runnung silver solder or braze into a well cleaned & fluxed seam. If it is a cut and shut type tank then but welding may be your only option.