Metal in the crank case

http://www.4shared.com/document/sMjNLzGr/2003_Yamaha_YZ250_FR_Wiring_Di.html

The link above is the wiring diagram from the 2003 Yamaha YZ250, but I am not sure if this will match the 1999 Yamaha YZ250.

Here is a link to the 1999 Yamaha YZ250 Service Manual, with the wiring diagrams: http://www.powersportresource.com/details.php?mID=237

It is less than $10.00, making it a great deal if the diagram I provided you doesn't match up.

I’m happy to help further over the phone at https://www.6ya.com/expert/jeremy_69f3cc28d95bf514

35 to 1 for fuel oil mix. if u r talking about crank case, i think 2 quarts, if there is a sight glass on side of cover, it should be right in center when bike is upright. If no sight and no leaks, just measure what you take out an add the exact same.

bearings to tite if you have oil injection I would try mixing it in your gas 1 air bubble will throw a bearing

Although your description isn't exactly the greatest, I assume you are referring to the power valve actuator. It fits into the side cover into a bearing near the waterpump. The gear on the oppposite end engages the end of the crankshaft when assembled. The actuator linkage engages into the slot near the middle of the gear assembly. Very difficult to explain but it takes just a few seconds to slip it into place. Nothing retains it during assembly, so be careful not to drop it.

Perhaps a visit to a site with an exploded view would help you - like Yamaha of Troys parts finder. It will provide you with an exploded view but possibly not the entire arrangement - this is what the manual is for.

A manual would show this arrangement. Google search "online manual YZ250"

NO!
the whole motor must be split