Fuel Tank Repair On Motorbike Or Any Other Vehicle
Ok, before i start i have to draw the line and make differentiations and clarification that there are some things and processes that designed by the book and 9 times out of the 10 they stay in the book, on another hand, there is a REAL life where things need to be done and they get done. The latest one is what drives the world, at least this is how i see it.
Here is walk through one of the projects that i did while back that i thought it will be interesting for people, as it is not an everyday sort of job.
So, there is a gentleman in Aberdeen who race motorbikes and he was preparing his bike for TT race. Now I am not a biker and definitely not a racer, but I take my hat off to you who is into it. Anyway back to the fuel tank, my customer wanted to use a fuel tank from a bigger cc bike on his small bike as it would give him longer time without refueling.
All work is done in his garage, (we provide mobile welding services too) the wall thickness is very thin, so to keep it the same and lightweight I used the lightest material that I had in stock and that happen to be 304-grade stainless steel 0.5mm thick that left over from the other project. The bottom part of the new tank was roundish and needed to be flattened out so it can fit on the smaller frame of the small bike.
Fuel tanks always and especially when they empty (Fumes are way more flammable then liquid!) are very dangerous to work with and present risk of explosion. Many different people try to overcome this problem by filling it up with the water. It never works that good, you always left with a little pocket of the air-fuel mix as if you fill it all of way up you will not be able to work on it. In addition to that, especially old cars fuel tanks have many baffles inside that makes impossible to get that water out of the tank when you finish. By many, it is a crap job that people do not want doing, due to a lot of hassle associated with it.
To me, a job is a job, I do those sort of things. First I totally diss like the idea of putting water inside of the fuel tank, instead, I fill it up with inert gas like Argon. As you probably know already and as you can see on this image in order for fire to exist, you must have 3 components. Oxygen, Fuel, and Heat are also known as the Fire Triangle. If we can eliminate one of them there will be no fire and in our case no fire, no BANG!!! Which is exactly what I need. To be honest I do not mind fire as long as it is outside of the tank. I actually prefer that any fumes ignite and burn right away instead of escape and form clouds that can be combusted after.
At all times when I do any sort of work on the fuel tank, I will purge it with inert gas first and never stop purging until the job is finished and cools down to the temperature that can not ignite the fumes. The image on the left shows you fuel tank with a clear pipe that is purging it with Argon. Any welding supply store will sale you Argon flow gauge that you can use to meter the flow of the gas in liters per minute, they are around £5. I want to create positive pressure with argon gas inside of the tank so that atmospheric oxygen cannot get in and cause the fire/explosion. Do not make too much pressure inside as if you do, it will start to blow holes as soon as you begin to weld and metal will get hot, it needs to be just above 1 atmosphere (normal air pressure (Could be more or less depends on your elevation)).
Next step once you purged tank with the gas is to cut out the bits that you do not need. Try to cut them out as one piece if possible as it will act as a template for you to cut new replacement part. I have a preference for making the second template on cardboard paper and then use it to see how it fit. This way I can trim it easy and mark areas that need to be extended so when I cut the final piece, it is as good as it is going to be.
Next, fit in your replacement part or expansion section, whatever you doing and tack it all as much as you need to make sure that it will not move and your gaps will not open up when you will be welding. As you can see I have lots of tags on this tank as my wall is only 0.5mm thick, any movement or gap increase will make my job a nightmare. Once it is welded and cool, stop purging and disconnect everything. Job is done.
I forgot to take a picture after it is being done as I was rushing home to beat the traffic.
Maybe next time! ????