Another question about my 79 YZ 250 - oil related

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Mar 12, 2001
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I want to change the oil in my 79 YZ 250. I found two drain bolts, but I didn't drain as much oil as I thought I should have.

The side of the case (right by the oil fill/dip stick) says "1100cc oil". I figured that converts to 1.16 qts. I went to drain it and it didn't drain that much. Do you think there are more than two drain plugs? I found another bolt which could be another drain, but it is on the left side of the bike under the front sprocket, it doesn't seem that it would drain anything that the other two on the bottom of the case would have already drained.

I am also having trouble finding which type oil to use. I use Mobil 1 15w-50 in my 01 YZ, but am not sure if this would be good for the 79. Any ideas? I am looking for a manual online, but only found a place that carries them in the UK. Do you think I can find one at a Yamaha dealer?

I took all the plastic off and airbox to check the filter and to look at the parts of the frame I couldn't see, and everything looks perfect. Even the entire engine looks pretty clean. I am impressed. I just want to make sure that this thing is maintained right before I hit a tree with it. =)

Sorry for all the questions, but I really don't want to do anything wrong with this thing.

Any help would be appreciated!