My friend just bought a unicycle of ebay…(after seeing how awesome they are 
)…and after pumping up the tyre with a bike pump, when she took the pump off, the valve (the little black thing inside) came off so now it won’t pump up…
Any advice? Can it be fixed?
New Tube
The valve stem core can be twisted out of a valve stem with the right tool. Like some of the 2 pronged tools seen here. Even fine needle nose pliers might work. But it shouldn’t come out by itself.
Maybe the stem wasn’t put together properly in the first place.
But if you have the inside core that came out, you might be able to twist it back in.
Here’s a picture that might help: schrader valve
A new tube should do the trick.
If the valve stem came out you can replace it, but really a valve stem shouldn’t liberate itself from a tube. That makes me think that there is something else wrong with the valve.
Thanks guys 
It turns out that (apparently) its a really rare type of valve (at least in the UK) which needs a special type of pump, so she’s just gonna replace the inner tube so she can use a bike pump instead.
A separate question from me: I was thinking of upgrading my total beginner tyre to this http://www.unicycle.uk.com/shop/shopdisplayproduct.asp?catalogid=572 , however do I need the inner tube? would it be any better or just a waste? Thanks again!
A good upgrade which is a hell of a lot cheaper than buying a trials uni with a 19" rim. Your existing tube should be fine.
In the short term, I wouldn’t bother changing the tyre. Once you get to hopping and dropping off things higher than a kerb then it’ll be worth while. You might actually find it harder to ride to start with than your current tyre.
With regard to the tube though, yes, you will need a high volume tube to fill it. Your current tube won’t be large enough.
One other thing… measure the distance between the forks on your unicycle to make sure this will fit without rubbing. It says it’s 2.4" wide, so you’ll need at least 2.5" to be safe.
STM
That probably means it’s a Woods valve:
In which case, you don’t need a special pump. Any pump that’s suitable for a Presta valve should do the job (most decent modern pumps can handle both Presta and Schrader valves), but it takes some getting used to. The trick, IIRC, is not to unscrew the valve before pumping.
If you have a presta valve you can go to some bike shop and see if they have a Presta/schrader valve adapter. It cost about $0.50 in Canada, I dont how much it is in UK but it’s really cheap. Or you can buy a new tube with the schrader valve
I think I’ll hold off buying the tyre for now then, however there would be enough room between hte forks unless the length of tyre from the rim upwards increases. Does this happen with bigger tyres?
And I’ll tell my friend to either have a go using the pump with the suggestion used or to buy a cheap adaptor…
