You would think that there is no way to write seven or eight paragraphs about inflating a tyre: you push air into it and that's it, isn't it?
Actually, is not that easy to inflate a racing tyre, at least in karts. It's worse when you use hard compounds.
Rims are "slanted", like this:
The tyre expands sideways when you inflate it. Because of this and the slant, the bead is larger than the rim when not inflated, so when you try to inflate it, there is a gap. If you use a regular or slightly "asthmatic" compressor, the air escapes through the gap. A foot pump won't do it, of course.
It's a catch-22 situation: the bead won't seat until the tyre inflates, but how do you inflate the tyre if the bead is not seated?
Do you see the gap? Try to inflate this with an electric pump!
Normally,
you have to remove the stem of the valve, for air to enter the tyre easily, while you seat the bead. Besides removing the stem, there are three ways to help the bead to seat, that I know:
1. Use a belt around the circumference to tighten the wheel (I'm dead serious).
2. Use a bead seal liquid (allow to dry before inflating), or, if the gap is small, use some other liquid. Some people around here uses liquid soap, which helps if the gap is not too large. If it is too large, you will get a lot of nice bubbles and no inflation. Of course, you have to lubricate the bead for it to seat easily, so, you'll need the soap anyway.
3. Use high pressure (be careful! protect yourself and I mean it) or, if you're desperate, a special mini-tank that provides you with more pressure (short bursts) called a "bead-seater".
Bead seater
Again, use all precautions if you use this method, because bead seaters are designed for truck tyres and a kart tyre is really small, so it will fill really quickly once you "overcome the gap".
Normally you use a combination of these three "methods", plus a lot of swearing...
I don't know if your problem is
because your mechanics used option number 2. Of course,
if this is the case, there is no problem with the bead sealing liquid heating and melting away when the tyre is already inflated. There is an easy way to know if this is the case: ask them!
If they used a bead seal liquid because of the tyre was junk (as J-Tom mentions), then, I think you should replace the rims (and the mechanics). You can kill yourself easily or worse, kill me (in the remote case that I'm racing against you
).
If you're using steel rims, you can repair them to make them round again, instead of using precarious sealing compounds. In spanish this repairment is called "to rectificate" (rectificar) the rim, I don't know the english term. Your tyre shop mechanic will use a special hammer (I think it's "softer" than the rim steel) and a tool designed to measure the roundness of the rims (a simple rotating table and a "finger" that moves across the rim to know if it's round).
BTW, some tyres have screws (normally three) around the rim. I have no idea why. Anyway, unscrew them before extracting the tyre and screw them before mounting it, but flush with the rim. Screw them completely once you've inserted the tyre.
It's a mistery to me why some kart rims have those screws (balancing?), but extract them before removing the tyre or you will ruin the bead
NOTE: after writing the post, I realized that the pictures I got show the guy mounting the tyre on a concrete surface: bad idea. Try to do it on a softer surface, I think you risk ruining the rims by scratching them.
