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 is some things and processes that designed by the book and 9 times out of the 10 they stay in the book, on other 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 done while back that i thought it will be interesting for people, as it is not a every day 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 done in his garage, (we provide mobile welding services too) the wall thickness is very thin, so to keep it the same and light weight i used 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. Bottom part of new tank was roundish and needed to be flattened out so it can fit on the smaller frame of small bike.
Fuel tanks always and specially 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 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 lots of hassle associated with it.
To me, job is a job so i do those sort of things. First i totally diss like 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 it is also known as 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 job is finished and cools down to the temperature that can not ignite the fumes. Image on the left shows you fuel tank with clear pipe that is purging it with Argon. Any welding supply store will sale you Argon flow gauge that you can use to meter 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 can not get in and cause the fire/explosion. Do not make too much pressure in side 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 of making second template on card board paper and then use it to see how it fit. This way i can trim it easy and mark areas that needs to be extended so when i cut final piece, it is as good as it is going to be.
Next, fit in your replacement part or expansion section, what ever 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 loots of tags on this tank as my wall is only 0.5mm thick, any movement or gap increase will make my life nightmare. Once it is welded and cool, stop purging ad disconnect everything. Job done.
I forgot to take picture after it is being done as i was rushing home to beat the traffic.
May be next time! ????