What causes compreesor to blow oil plug and breather filter while running

Question edited for clarity.
Question moved to Buell Blast.

On a bike with no service history it would be standard practice to change oil and filter.

It seems to be a known issue.

https://www.google.com/search?q=2002+buell+blast+spitting+oil+from+the+crank+case+breather

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What is the compression ratio for my engine?

Briggs & Stratton side valve (L-Head) engines use a compression ratio of 6 to 1.Our Overhead Valve (OHV) engines use a compression ratio of 8.5 to 1.

What would cause my engine to "puff" smoke while it runs?

White/blue smoking usually indicates the burning of oil. Causes to this condition include:

• Overfilling the crankcase with oil
• Incorrect oil grade
• Operating engine at greater than a 15 degree angle
• Inoperative crankcase breather
• Crankcase air leak
• Blown head gasket
• Worn cylinder and/or rings
• Turning/Tilting the engine on its side for any reason (storage, changing oil, etc). If the engine has to be tilted, ensure the spark plug is facing upwards to help prevent oil from escaping the crankcase.

Also, be aware that any small air leak can cause an excess of air entering the crankcase and will create a higher oil mist than the breather is capable of handling. The excess oil will then return through the breather tube and back to the air filter. Engine oil capacity is dependant on your specific engine model. To determine your engine's oil capacity, please visit our Oil Capacitypage. Oil level checking and changing intervals are available on ourMaintenance Schedule page, as well as a hyperlink (text highlighted in blue) leading to oil changing procedures.
The "Oil" section of your Operator's Manual also contains this information. Other possible causes include operating or tilting the unit at an angle, an obstruction in the breather tube (located behind the air filter), damage to the cylinder/piston rings, etc.

Your oil breather (on the side of the engine opposite the carb) may be malfunctioning/defective allowing the carb to **** oil from it. There is a breather tube that crosses over the top of the cylinder connecting the crankcase( oil) breather to the air filter housing. Check the oil level and the condition of the air filter and esp. the oil breather. It serves the same function as a PCV on a car engine.

How many miles do you have? You probably need to have your oil pump alligned. They get out of wack and cause over oiling. I believe it caused by not being able to return oil efficiently. An evo tappet block alignment tool is now used to align the TC internal oil pump.

hi 81 yamaha i am concerned about the fuel smell coming out with the oil. could be the carbs flooding filling your crankcase with fuel? if not it sounds like you have blow by which would cause your crank case to be slightly pressured. this is caused by worn piston rings. do not plug your crank vent. if you leave your vent open install small filter to stop dirt from entering jim

Often times there is a engine breather tube that has to do with emissions that runs from the engine to the air filter breather box. This tube can in some cases blow oil through it when the engine is run hard. Make sure you're not over filling the engine with oil when you change it because this will cause the oil to "blow off" the excess and the air box is where it often goes.
There is also another possibility, are you using too much oil in your air filter after you clean it? This too is a common cause for oil in the air box, if that's the case I would not worry about it.
The last case scenario is one you don't want, that would be washed out rings which cause blow by and that in turn causes the engine to blow oil out of the breather tube which I'm confident it venting into the air box.
Please let me know if these resolve your question and if not give me more details and I will be happy to assist you further.
Regards,
RSelvy

This is a common problem on all sportsters, they have an oil blow by that dumps it into the air filter. I have found that if I run about a half quart low the problem goes away.