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Oil drains from reserves

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I have a 2002 yamaha yz 250 f and I just finished a full top and bottom end rebuild on the bike.

I installed all new O rings and gaskets on the motor but the problem I'm having is that when the bike sits over night and I go to cheak the oil the next day the dipstick is dry. But when I start the bike and warm it up the oil level is at the full line. It seems like it's draining into the crank case. Is this bad for the motor? And what can I do to fix the problem?

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Sounds normal.

This is why you check the oil level shortly after shutting the engine off.

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I always check the oil after I warm the bike up and shut it off but I didn't know if it was a big problem or not that it all drained into the case

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Normal. This design runs a dry sump, it reduces drag on the crankshaft, saves space, and cools the oil. They do that by having a pump system and oil tank. The pump primes and takes oil drained into the sump up to the tank and holds system pressure to lube the crank, piston, cams, and tranny. Don't overfill. Just fill with 1.25 qts., check level after running and make sure its to the upper level, and change oil after 5 hrs of run time. Be anal about oil / filter changes, and it'll be reliable. Skip oil changes and expect expensive repairs in a short time. These are highly stressed race bikes, and the oil gets hot and the molecules get sheared, so the protection breaks down.

http://www.thumpertalk.com/topic/51313-forum-faq-read-before-you-post/

Edited by ronbuell

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Cool thanks bud! This is my first 4-stroke race bike so I'm learning lots in a hurry. like you say there are huge stresses on this bike which I'm not usto. unlike an honda xr250. Thoes bikes seem bullet proof!

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