Yamaha T50 gas in the crankcase!

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carolinaskiffman

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Hi, we have a Yamaha T50 4 stroke 2007 and we keep getting gas in the crankcase, ALOT.... Anyone know what might be causing this? We just changed all the oil, filters, fuel hoses with ethenol resis fuel lines. And drained the gas and started with fresh non-ethenol fuel. Ran great last weekend in driveway. Was goin to run with hose this weekend before taking out and pulled dipstick and it was fuel all..... the way with fuel.
 
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extreme01

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Re: Yamaha T50 gas in the crankcase!

well anytime i ever seen fuel in the oil when the engine is just sitting tells me a float is stuck down or sunk
 
Don S

Don S

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Re: Yamaha T50 gas in the crankcase!

It may not sound like this would cause it, but a faulty thermostat what doesn't allow the engine to warm up will cause gas in the oil as well.
 
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99yam40

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Re: Yamaha T50 gas in the crankcase!

I would not think running it in the driveway on hose for a little while would cause oil to get that contaminated with fuel from stuck stat, but I could be wrong.

How long did it run?
 
Don S

Don S

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Re: Yamaha T50 gas in the crankcase!

I read the "Ran great last weekend" part, and completely spaced out the "in driveway" part.

About a 99% chance it's a bad pump, unless he ran it all weekend in the driveway.
 
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Capt Ken

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Re: Yamaha T50 gas in the crankcase!

That pump uses a plunger off the cam and not intake pressure. Don't believe it can leak back into the engine. if he is filling the oil to the top oil mark, it can make oil and the level increase. It may not be fuel in the oil.
 
Don S

Don S

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Re: Yamaha T50 gas in the crankcase!

The pump is mounted on the valve cover, and if the fuel pump diaphragm (item #25 in the link below) is ruptured, it will pump fuel directly into the valve cover, and on into the crankcase.

Yamaha Part Catalog

A full model number would be VERY helpful at this point.
 
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Capt Ken

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Re: Yamaha T50 gas in the crankcase!

It could be possible but I have never seen one leak past the plunger.
 
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carolinaskiffman

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Re: Yamaha T50 gas in the crankcase!

Well here is the info off the engine 2006 Yamaha T50TLR
6c2 L 1005036 , any help is appreciated Thanks...





Don S said:
The pump is mounted on the valve cover, and if the fuel pump diaphragm (item #25 in the link below) is ruptured, it will pump fuel directly into the valve cover, and on into the crankcase.

Yamaha Part Catalog

A full model number would be VERY helpful at this point.
Click to expand...
 
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carolinaskiffman

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Dec 15, 2012
Messages
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Re: Yamaha T50 gas in the crankcase!

Pulled dipstick out today to check, and fuel/oil came out the dipstick port like a hose shooting straight up, what a mess....





carolinaskiffman said:
Hi, we have a Yamaha T50 4 stroke 2007 and we keep getting gas in the crankcase, ALOT.... Anyone know what might be causing this? We just changed all the oil, filters, fuel hoses with ethenol resis fuel lines. And drained the gas and started with fresh non-ethenol fuel. Ran great last weekend in driveway. Was goin to run with hose this weekend before taking out and pulled dipstick and it was fuel all..... the way with fuel.
Click to expand...
 
Don S

Don S

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62,321
Re: Yamaha T50 gas in the crankcase!

Have you checked the pump? Take it off the valve cover (leave the hoses hooked up), pump the squeeze bulb to build pressure and while it's pressurized, look at the push rod of the pump and see if gas is coming out. Push in on the plunger a few times too.
 
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