Here's is how I go about it.
Having a tube of the old Tufo sealant or new formula for repair, a needle nose plier or that plastic key to remove valve cores that come with some Tufo extenders handy:
- If on a low profile rim or using an extender that has the core moved to its top, no need to remove the tubular.
- Remove the core with a dedicated tool or a small needle nose plier.
- Turn the wheel so the stem is at about five o'clock. Point being that if at six o'clock the stem will squash the inner tube so no liquid can enter it.
- Next I use the plastic spout top of a Vittoria Pittstop as a means to hold some of the liquid latex whilst it enters the inner tube. You don't really need it but it makes it easier to fill the inner tube.
- Now follow some tricky parts: you'd want to get some liquid into that inner tube so you slowly fill the valve stem with liquid latex.
Once you notice the valve stem is empty, you once again carefully pour in some more. Repeat untill you have about 10ml in the tube, 1/7th of the tube's content.
We're talking small quantities here.
- Now whipe the valve stem clean and quickly mount the core and tighten it.
- Inflate to about 1/2 bar, just enough to make the tubular look roundish again and spin the wheel around to let the liquid disperse inside the inner tube.
- Reinflate the tubular slowly to about 6 bar and spin the wheel around again. if you can hear air escaping try to locate the leak and put a finger on it. This will give the liquid sufficient time to set and block the hole.
- Assuming no more air is leaking reinflate again to normal operating pressure (say about 100 psi) and leave it like that for an hour or so.
- Check if the leak was successfully stopped and again inflate to about half a bar over beyond normal inflation to simulate normal road conditions as seen by the tubular.
- Recheck the next day. If the tyre has retained normal pressure (i.e. no abnormal loss of air), you're good to go. If not you'll need to repeat the process. (Rare IME)
-Now you'd ideally want to keep this tyre inflated and in use for the next couple of days at least to leave enough time for all the fluid you poured in to solidify.
Accidentally deflating it may well cog up the core with liquid latex which can be washed out with White Spirit.
Needless to say, a worn tube is just that. You may well pull some extra miles out of but why bother?
Too big a hole is too big a hole. No miracle cures for those.