You were feeling nostalgic and began scouring the classifieds to find the bike of your youth – a bike that’s the same model and maybe the same year as the first bike you owned, a few decades ago. Maybe it was a barn find; maybe it was a bike you heard about from a friend, discovered sitting idle in a garage for a long time. Regardless of where you found your hidden treasure, chances are it was resting for many years without running.

If so, the first thing that will probably need attention is the fuel system. Since it’s an older bike, that means it will be carbureted, so this will include, aside from the carburetors, the fuel tank, fuel lines and gas tank. A look into the gas tank of your newly acquired dusty gem might reveal a rusty interior. The carburetors are probably gummed up inside. The petcock might be jammed tight or leaking.

We’ll start with the fuel tank. After draining the fuel tank, using a flashlight, look carefully as far inside as you can. To look deeper into the tank, you can use a small, telescopic mirror. If there’s only light surface rust in spots, chances are the tank won’t need further attention. However, if you see rust all over, and especially flaking, you’ll have to clean it out to prevent problems elsewhere in the fuel system, as rust flakes can work their way downstream.

After removing the fuel tank, you can eliminate most of the corrosion by using a method I’ve employed with great success in the past. Some old-school mechanics used to add handfuls of nuts and bolts into the tank with some solvent, like Varsol, and shake it up to remove rust. No need for that; after leaving the fuel tank to dry for several hours with the gas cap removed, I recommend adding a litre of CLR, a product that removes calcium, lime and rust, and working it around to cover the entire inner surface of the fuel tank. Let the tank sit for several hours while agitating it occasionally to keep the tank walls soaked.

This stuff will dissolve the rust. If, after inspecting the tank, you see bare metal – and if you’re patient, you will – drain the CLR and wash the inside of the fuel tank with cold water. Although this might seem counterintuitive, as bare metal will rust easily, there are other steps to take to prevent this from happening.

After thoroughly rinsing the tank with water and draining it, add a bottle of gas-line antifreeze. By sloshing this alcohol-based product around and then draining it, you will effectively remove all remaining water from the tank. At this point, if you see leaks because of perforation, you’ll have to get the tank repaired by a professional – or find another one.

Barring any leaks, let the fuel tank sit for several minutes with the gas cap open to allow the quickly evaporating gas-line antifreeze to dry, and then apply a liberal coat of WD40 to the interior. WD40 will displace any remaining water left in the tank, and its lubricating qualities will prevent further corrosion from taking place. Your tank is now ready for fuel, though you may want to install an inline fuel filter to catch any stray rust.

There are products designed to coat the inside of the fuel tank to prevent rust, and to seal it if it has leaks, but I have yet to find one that is easy to apply and that works as claimed. If you want to prevent rust from coming back, keep your tank full as often as you can and add a bottle of gas-line antifreeze occasionally to keep the accumulation of water at bay. In winter, drain it of fuel and coat it with WD40.

Whether the petcock is vacuum-operated or not, replacement parts are available to repair it if it leaks. You can source the parts through OEM dealers; also, complete rebuild kits are available for many petcock types from aftermarket suppliers. Repairing a petcock is simply a matter of disassembling it, cleaning it and reassembling it with new O-rings and gaskets.

In carburetors, stale fuel will plug jets and jam float needles in their bores; it also corrodes the float-needle seats. You will need a service manual to disassemble the carburetors – and take note of jet sizes and locations as you take them apart. Place all of the metal components into a container and spray aerosol carburetor cleaner, available in auto parts stores, into the container until all the parts are immersed. Let them soak for several hours, after which they will emerge like new. The pilot jets might need extra attention, as the small holes could require further cleaning. You can use a couple of strands pulled from copper electrical wire and twisted together to clean the jet bores, but be very careful cleaning jets. Copper is soft and won’t damage the jet if you are cautious, whereas anything harder could easily change the size of the jet orifice.

Screw-in float-needle seats are usually replaceable, but in some carburetors they are pressed in and not serviceable. If the needle seats are pitted and not replaceable, you can use tiny ball bearings, like the ones in bicycle wheels, to refresh them. You simply drop a single ball bearing into the needle seat, and with a small hammer and punch, lightly tap onto the ball to renew the seating surface. Like the petcock components, new float needles are available through various suppliers.

Use a plastic extension on the aerosol carb cleaner to spray it into the passages of the carb body. It will spew out of other passages as it works its way through the carburetor, so wear eye protection and work in a well-ventilated area. If an air compressor isn’t available, use bottled compressed air, available in computer shops, to blow out the passages.

After adjusting the float levels to spec, reassemble the carburetors and fill them with fuel before installing them on the bike, to make sure they don’t leak. Replace dry, cracked fuel lines with proper fuel hose, available in auto parts stores, and after reinstalling the carburetors and fuel tank, you will be ready to fire up your new, old bike. That is, of course, if there are no electrical issues . . .

Technical articles are written purely as reference only and your motorcycle may require different procedures. You should be mechanically inclined to carry out your own maintenance and we recommend you contact your mechanic prior to performing any type of work on your bike.