I dont know what dirtbike i have?

Lisa, is it possible the numbers were wrote down but are faded, if so and it is very important for you to have this info. a police forensic lab can probably do it.
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It's a 2004. I have an MXF-150-4N that 4N is the manufacture date apparently.

Just by looking at the vin number won't tell you the year of your bike. You need to write the vin number down and get on the phone with a dealer that operates your type of motorcycle manufacture. Tell them the vin number and then they can tell you what year it is.

EXCEPT If it isn't older than a 1983 you can use this method on all 17 digit vin numbers cars, bikes, atv's etc. code follows,count to the tenth digit,D IS 1983 E 84. F 85. G 86.H 87.J 88.K 89.L 90.M 91. N 92.P 93.R 94. S 95.T 96.V 97. W 98.X 99.Y 2000. 1 01. 2 02.3 03. 4 04. 5 05. 6 06.7 07. You sholdn't have any problem understanding this.

Read more: http://wiki.answers.com/Q/What_numbers_in_the_vin_is_the_year#ixzz1C6hugrVK

Go to this free website and you can enter the VIN and get all sorts of info on your bike. Please rate my answer. Thanks!
http://www.motoverse.com/tools/vin/yamaha.asp

http://www.motoverse.com/tools/vinDecoder.asp

This link provved right with your VIN...take it from there or check the site below for other YAMAHA numbers you may need. Let me know below if it's usefull, Cheers.

http://www.boats.net/parts/search/Yamaha/Motorcycle/1993/YZ125E/parts.html

Locate the VIN on the front of the frame if it's still there. Then try this site to break it down: http://www.motorcycle-journal.com/forum/tips-training/5800-how-decode-vin-number.html

SCRAPE OF THE PAINT RIGHT SIDE OF GOOSE NECK

I'm not 100% sure because I have'nt had much dealings with yamaha dirtbikes but I do know that on Hondas and Kawasakis there are no rod caps to remove the rod from the crank, the crankshaft actually splits and the rod slips off. They are a very tight press fit and have to be reassemled perfectly or it will throw the whole balance of the engine off. I recommend taking it to the dealer and letting them do it. I know that on my Honda CR 125 instead of trying to replace the lower rod bearing I was able to purchase a crankshaft with a new rod already attached. Hope this was helpful.

It should be located on the right hand side of the down tube. Turn the handle bars to the left and look on the right side of the down tube. If it is not there or has been filed off most likely it is hot.