Fuel Leak From Carb

[Liono]

I'm starting to seriously consider selling my bike now, after 6 weeks in the garage I had it back for 6 days before something went wrong again
In the morning I rode into work fine and the bike seemed to be running nicely. At the end of the day I turned the fuel on and went to start the bike. Just before I pressed the starter I noticed that there was a strong smell of petrol, looked down and saw that fuel was dripping quickly out of the bottom of the bike. Closer inspection revealed that the fuel was coming out of an opening in the carb. There are two 'holes' in the carb, one above the other, the top one has a screw in it that looks like it would be adjustable, and the fuel was coming out of the one at the bottom. Does anyone have any ideas on what is causing this? I work in a school, so it is a possibility that one of the kids had a fiddle with it, although I don't think that this is too likely.
Oh, and the bike is a TDR 125 if that makes any difference.

[G]

It may be the carb drain bit, left slightly open.

If that's the case, you just need to do it up. However keep a note of how many times you turn it, incase it's something like an idle adjuster and you need to reset it.

Was the garage doing stuff with the carb? If so, get them to sort it and shout at them a bit.
One of the reasons I rarely trust 'professional' mechanics.

[stinkwheel]

Try tapping the side of the float bowl with a nylon hammer or a bit of wood, the symptoms you describe can be due to a sticking float and the tapping 'unsticks' it. You would know if this is the case as the flow of fuel would stop after the tapping.

It can start again but repeated tapping usually sorts it out. Either way, it sounds to me like the fuel is coming out of the overflow in the float bowl, reasons for this (in decending order of likleyhood) include:

Sticking float.
Dirt or grit in needle valve.
Leaking float (so it doesn't float).
Damaged needle valve or seat.

Also possibly incorrect float height, this is fixed on most bikes these days and in my experience does not alter itself but if someone has been messing with it...

There was a similar probem on THIS THREAD which also has a link to a good exploded diagram of a carburettor, yours may be slightly different but the float bowl assembly should be similar.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Liono]

Hitting things with bits of wood - that's the kind of fixing that even I can do I will have a go at that on Monday. It does sound like something has got stuck internally then, I just remembered that I had to switch to reserve a day or two before, so it could be some gunk out of the tank bunging things up.

[stinkwheel]

Well that is quite a coincidence then. As I remember the bike was off the road for a fairly long period before you got it too? So the reserve may not have been used for quite some time.

If you find it was muck getting stuck in the needle valve, fit an inline fuel filter (cost pennies) before you switch the fuel back on.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Liono]

Thanks for all of the help, I now have the bike running again

After a couple of taps to the carb it worked nicely, although I don't know why there was muck in the tank as I had to run it on the reserve position for a week or so a while ago (as a result of one of the previous problems!) so that should have cleared most of it out.

Normally when I start the bike I don't touch the throttle, but to get it started after clearing the carb I had to have the throttle on full, which puzzled me. Any ideas why this should have been the case?