Hi there,
On the Bet & Win 150, it's really not that bad getting to the carburetor. The seat is all you really have to remove, and if I remember correctly it's only a few 10mm bolts, the battery and a fuse box. Perhaps an underseat light, but it's been a while since I've messed with it.
The tricky part, if you haven't done it before, is the carburetor. Just to quickly purge the main jet though, here's a simple trick that you can do without even taking the seat off.
Open up your seat, and empty it. You should see a carburetor access hatch on the bottom. Take this off, and then you can see the carburetor. There is a brass colored cap (sometimes it's black plastic though) on the top of the carburetor. This holds the diaphragm, slide and needle. If you remove the cap (the screws can be a bugger) and then lift the diaphragm up and out (Needle and slide will be attached) you can simply spray a small bit of carburetor cleaner straight down into the atomizer, which is the hole that the needle will have come out of. Many times, it's just a little gummed up, and this short blast of carb cleaner can clear it up without the need to take the whole carb apart. You can follow through with compressed air if you like, but only very lightly.
The above method will work if the main jet is a little blocked up from gas beginning to tarnish. If you actually have water or trash in the fuel though, you'll have to take it apart and give it the works.
I've got some pictures of a similar carburetor around here somewhere, I'll have to find them.
Where are you from Scooter_NOT_Libby?
Cheers!
~Josh