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Engine Tech
Engine Tech, Engine Technician
Category: Small Engine
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Experience:  Over 20yrs of experience in small engine repair.
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i have an 87 yamaha moto 4 80cc there is a tube that comes

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i have an 87 yamaha moto 4 80cc there is a tube that comes out of the transmission i believe. directly behind the motor.that oil is coming out of. iam wondering the cause and fix to this problem. thank you for your time
Submitted: 4 years ago.
Category: Small Engine
Expert:  Engine Tech replied 4 years ago.
Hello and thank you for using this service,

That tube is the breather tube for the engine. The cause for the oil is typically an indication of worn piston rings. What happens is poor compression causes blow by. That loss of compression in the cyclinder creates the back pressure in the crancase and forces oil out the breather tube. If you do a cyclinger compression test you will most likely find that the compression is low. Now you can try and put a siphon break on the crankcase breather. If the blow by is to much it will still leak so still that is just a temporary fix. Do a compression test and see 175PSI is normal so if you are seeing 120 or less that is not good.

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