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The petrol tank is a simple plastic container (a very hard plastic and which cannot be damaged by the petrol contact) which has the task of keeping inside the petrol. It always has a quite complex shape since it has to stick between the steering-wheel support and its steering column, while in the front part it is screwed to the metallic plate. From the top part two small pipes go out. The first pipe has a function of recovering the petrol in case of coming out from the top part (if the petrol tank is too full): this small pipe brings the liquide to another small container which is put a bit above it and which is connected to the petrol tank through another small pipe, in a way the petrol can come back. The second small pipe has 2 different ends, one end goes to the carburetor, the other one has attached a piece of metal which is a kind of weight, so that almost all petrol in the tank can be used. It’s very important this small pipe touches the bottom, on the other hand when you are in situation of little petrol in the tank, you could risk to have some “empty” of petrol and to seize (that is because the quantity of petrol decreases, so the ratio air/petrol increases and it causes combustion temperature increasing). This pipe can be used for the tank empty: it’s enough detaching it from the carburetor and bringing it to a height lower than the carburetor base’s one, so the communicating vessels principle can work (putting the contents in another container). ATTENTION: since you have to leave the pipe detached during repairing, remember to use an adhesive tape to keep the pipe at a height higher than the carburetor’s one. A last hole is used for the fuelling:
to perform this operation is better putting the kart on the ground
instead on the carriage and it’s better using a specific funnel
(better if it’s long and with a small filter, generally sold
as funnel for cars’ oil), instead of a regular kitchen’s
one. It’s not comfortable put the petrol directly from the
tank. It’s better if the tank has a bigger volume than the
fuel, so you can avoid fuel lost during the operation; based on
the law, it’s necessary the use of an iron ratified tank,
even if the plastic one is more comfortable and handy (a petrol
pump attendant could refuse to insert petrol in a not ratified tank).
We could start saying there are different kind of petroil: in fact it can be made by leaded petrol or unleaded petrol and the percentage of oil can vary. In the125 category, a correct percentage of oil can be 5%, in 100 it can be around 6-7%; the perfect percentage for these last ones is 6, but if you want to save old engines or if you want to be sure not to break the engine in extreme situations, it’s better having a 7%. I personally have a 7%, and it’s the percentage I suggest to all people who are at a “beginner” level in driving a kart and maybe have engines not so new….let’s say 1% more, it could compensate a temperature increase, and a consequent piston dilation. Let’s now examine closely this subject. In theory, petroil which guarantees best performance would be with a 0% of oil (with unleaded petrol, as we will see); obviously with this kind of petroil you could drive 30 mt, at the MIN rpm, before seizing. The oil as a very important function in lubrication and enters the cylinder together with the petrol; this dense liquide enables a good sliding between 2 parts (piston and cylinder) and, in particular with high temperatures and rpm, it could become problematical, because of a very low tolerance between piston and cylinder. The oil is not burnt (or it is burnt very bad and with a very low efficiency for the engine) and so it causes a worsening in petrol combustion; in addition to this, the oil is very polluting. The smoke going out the kart exhausts, it’s very often due to the not correct oil combustion, especially when the engine is cold. A high oil percentage in the petroil, could cause the engine flooding. If you have an engine to be run in, it’s better beginning with an oil percentage very close to the 7%, and then gradually decreasing it. In the 125 category, I think they all use a 5%, in fact with this engine displacement, engines are safer and more secure. It’s also very important using oil which is suitable for karts or anyhow for races. Concerning petrol (leaded or unleaded), the petrol which allows you reaching the best performance is the leaded one, and it’s also long lasting and gives you a high degree of safety and the best use. So it would be better using the leaded one. So why we are saying “it would be”? Because during races it’s compulsory using the unleaded petrol for “pollution” reasons, even if it’s a stupid thing: in fact without a catalyst and a proper engine, the unleaded petrol is worse and more harmful than the leaded one! If the problem appears it would be a trouble: the leaded one pollutes a lot, but the unleaded one even more! So what? What to be used? Air? Well, it’s better not to think to a problem which is not our problem… Let’s consider in a short while the leaded petrol won’t be sold anymore, so it’s better start using the unleaded one as soon as possible, in order of being used with that one. In addition to this, all kinds of lubricating oils are better utilized with the unleaded petrol. You should know changing petrol from the leaded to the unleaded one or vice versa doesn’t require special shrewdness: there are people saying you could even mix both petrol, but my advice is not to do that. So in order of changing petrol, you have to use your kart until your petrol tank is almost empty, then detach the pipe from the carburetor and insert in an empty container, until the complete emptying of the petrol tank. Now you can connect again the pipe, fill the tank with the new type of petrol, and “recharge” the petrol (in a way I will tell you later); there are people who say you need to grease the carburetion when you use the unleaded petrol: I don’t know if it’s true, but you could do it, just to stay safer, then regulate again the carburetion, starting from this basic regulation. Actually I’ve been greasing it since I’m using the unleaded petrol. Recharging the petrol means filling
the pipe which brings the petrol from the tank to the carburetor
and let it enter the carburetor itself. To do it, you have to slacken
the sparking plug (in order of decreasing the pressure/compression)
but not to remove it, because in this way it could have a cover
lack in closing the air entry; then the filter has to be detached,
with one hand you have to close up the carburetor entry and with
the other one you have to turn the back wheels; if you are in two
people the operation can be faster, since one person can keep the
filter closed and the other one turns the wheels. As soon as the
petrol falls in the carburetor pipe (and it’s visible in the
carburetor itself), the operation is concluded and after a while
the kart push should start (of course after reassembling the filter
and tightening the sparking plugs). If you want you could leave
everything assembled, and another person could push you and your
kart for a stretch, keeping one hand on the filter, and when the
petrol reaches the carburetor, take away the hand from the filter;
the problem is that the operation here mentioned is quite tiring
for the person who is pushing.
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