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Discussion Starter #1
Hi, I recently got a '81 Yamaha SR250 project. Needed some parts and cleaning but I've got it starting and running very nicely, except for the fact that while accelerating it's blowing ALOT of oil out the crank case breather tube. Like to the point of emptying the crank case! I drained the original oil (which was really just drops, more from the filter opening than the case), put a fresh quart in, rode twice for maybe 20 minutes each time and I'm empty again and the back of the bike is covered in oil!

I read somewhere about a pressure relief valve and filter screen in the pan area of some of the bigger SR's getting clogged and after being fixed solved the problem. I can't find any kind of valve in the schematics for this bike, and it looks like there's no pan to drop to clean.

Any ideas? Should I pull the engine and crack the case? There is a large (say 17-19mm) nut surrounded by a circle of what looks like small radiator fins fanning out from it on the opposite side of the bottom of the case from the oil drain plug...can't find what that is for on the schematic.

Other than this, the bike runs really nicely! Thanks for reading, happy memorial day, and thank you for your service!
 

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Discussion Starter #2
Update: I removed the large round cap on the bottom of the crank and voila, there's the rest of my oil. Why would I have nothing coming out of the drain and all the rest of the oil in the other half of the crank case?
 

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Discussion Starter #4
Found some photos, with a search for "81 Yamaha SR250 oil drain"; seems the large bolt with the fins around it IS the drain. I can't tell what the other bolt is for, but from the casting around it, it certainly won't drain much, if any, oil.

Thanks for the reply. It sure is.... WHOOSH...I found the rest of the oil in quick fashion! That's the biggest drain plug I've ever seen. I'm 99% sure I was just overfilled now. I'll let you know this evening....
 

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Dang. That plug is nearly bigger than the bike.:D I've never owned a Yami so that's interesting to me.
 

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Discussion Starter #6
Victory! No oil blowout. Was definitely overfilled. Thanks for the suggestions! It's been a blast reviving and dolling her up. I have some straight bars coming Tuesday, maybe I'll have enough posts by then to post ya a pic :thumbsup:
 

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Discussion Starter #7
Victory! No oil blowout. Was definitely overfilled. Thanks for the suggestions! It's been a blast reviving and dolling her up. I have some straight bars coming Tuesday, maybe I'll have enough posts by then to post ya a pic :thumbsup:
Well I broke the threshold and I said I'd post a pic...so here you go!





 

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Retired twice: Navy and as a govt contractor
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nice
 
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