I'm currently rebuilding my 77 dt250. I have the cases separated and the crankshaft is in the left side case along with the transmission. I was using my clymer manual to guide me through it but it stops short of removing the crankshaft from the left side. In the manual it says to take it to a dealer or a machinist. I've only done this once before on a smaller bike and it was fine. Is there some reason I shouldn't do this? Additionally is there any measurements I should take before I remove it or measurements I should know before I resinstall it. I'm specifically concerned about when I press the shaft back into the left side knowing how deep it is to go. 

Secondly the manual says the transmission should come out easily. I removed the shift drum and shift forks but the side of hte transmission that is connected directly to the output shaft that gets the drive sprocket connected is not wanting to budge. I noticed a plate beneath the transmission around this shaft that looks liek its supposed to hold the seal in place. I cannot remove it before the transmission as the screws back into the first gear. What am I missing here? 

Lastly is there another good manual that wont cost me a fortune? The factory service manual in the tech library does not elaborate much here. 

Thank you!

The shaft is stuck in the bearing, use your case splitter or basic harmonic ballancer puller to push out the crank , a  hydrolic press will work also , the main bearing will probably come out still  on the crank, use a bearing puller to get it off, I've set the cases on a hot plate to warm and expand the clearance , sometimes this is enough for the bearings to fall out on their own, careful with the transmission don't use the press , careful rubber mallet and the hot plate possibly

Bumping for visibility. If anyone has any information regarding a better manual please let me know.

www.yamaha-enduros.com/index.php/service...ctory-service-manual

and there is a supplement there too 

I already looked through them they don't provide me with answers either.

Page 23 of the Factory Service manual in the Tech Library describes and has a picture of the crank being pressed out of the case. 

I'm not quite sure what you're describing with the trans?  There is a bearing retainer inside the case under the sprocket.  It does not need to be removed.  The sprocket and spacer on the outside of the case do need to be removed.  But first gear is on the clutch side of the output shaft and there is no seal there.  The only trans shaft seal is under the sprocket.  On the clutch side the kick idler needs to come off, again, outside the center cases.