On a 2000 YZ 250 where can i find the dip stick for the oil i need to change it ?

That bike doesn't have a dipstick. It has an oil level check bolt on the right crankcase cover (it has a sealing washer on it). http://www.bikebandit.com/parts/ Go to - your bike - Crankcase Cover 1 - # 20 When checking the oil level and filling the crankcase, hold the bike upright. Drain the oil and install the drain bolt with a new crush washer if necessary. Remove the oil level check bolt and put a drain pan under it. Fill the crankcase (slowly) until oil starts to drain out of the check bolt. Re-install the check bolt, start and run the engine for a few minutes (to let the oil coat the internal parts). Turn off the engine and let it sit for a few minutes (to let the oil settle in the bottom of the crankcase). Hold the bike upright and remove the check bolt. Add oil until it starts to drain out of the hole. When the oil stops draining, it's at the proper level. Install the check bolt.