Fouling plugs just put new float and needle valve in a carburator on a 2000 yz 125 and it is fouling plugs

This can be caused by all sorts of things.There is no real order of probability so I'll just list them.Your oil/fuel ratio could be rich depending on what oil you use,your powervalve could be stuck closed(pop off the plastic cover over the actuator located at the front of the clutch cover,its held in place by 3 screws attached to the barrel,start the bike and give it a big blat on the throttle and see if the lever moves)it could have a blown crank seal(the symptom displayed by this fault is that you will be using gearbox oil),the expansion chamber could be carboned up,or the piston and/or rings could be worn.If all these things check out ok I suggest either raising the clip on the needle(which drops the needle causing the mixture to run slightly leaner) If this does not have enough effect go down one size in the main jet.Adjusting the main jet size will require you initally to very frequently remove the spark plug to check that you haven't gone too lean. The plug should not be wet and oily,the perfect colour is a tan colour and not wet.I must stress that jetting a 2 stroke if you lack experience can be tricky in that if you go too lean you can seize the engine so if you do reduce the size of your main jet frequent initall inspections of the plug is highly recommended.As a final note,if you are using a standard plug and not a racing plug(ie gold paladnium or irridium)thay are inherently more susseptable to fouling & changing to a "racing plug" may help to reduce your plug fouling.Hope this was helpfull