i picked up a 98 v-max with a blown motor , rod bearing appear to be puked. after i pulled the motor i noticed the liquid in the oil bottle was very thin , almost to thin to be oil. i dumped it out and it appeared to be almost straight gas. my question is i really really dont believe the previous owner filled the oil bottle with gas (posible but doubtful i hope) but could a bad oil pump cause this ? is there any way for gas to bleed back to the oil tank ?
Snowbear
New member
Can't see how. it would take a lot of back pressure but you say the motor blew? Maybe the previous owner bought the sled filled the oil tank with gas and pow there you have it. when you peel the motor apart you will see.
once i pulled the motor out and apart it looks like the bottom end is done. just cant believe someone would fill the oil tank with gas. just wondering if there is any other possible way for it to get in there other than by pure stupidity.
Maybe excessive blow by causing gas from crankcase to return to the oil reservoir...??
sleddineinar
VIP Member
Anything is possible! Last year my brother bought a burned up sled, the previous owner put plain old motor oil in the oil tank. You could smell it when we took the motor apart, it was definately motor when we emptied the oil tank out!
i havent figured it out but i really dont have the funds or the patience to put a motor in it and have the same thing happen. figures id ask guys who have been around these and seen everything if there is a possible explanation for this. now i just gotta find a good 600 two lunger.
I was pretty sure that it is possible to have a fuel pump problem and have the gas back fill the oil tank. The gas and oil are blended in the fuel pump before delivery to the carbs.
crewchief47 said:
thats the lines i was thinking along. never seen it myself but dont know if its even possible. maybe a fresh motor is deserving of a new pump in this case just to be safe.
Maybe was waterskippin' and used the oil tank for fuel tank ??
OnDaTrail
New member
A guy brought me a 4 stroke engine once that was smoking badly. I checked the oil and found gas in it. Thinking he had a bad float valve which allowed the gas to drain through to the crankcase, I fixed that and changed the oil. To my surprise, it still smoked awful. Turned out he had put gas in the crankcase and oil in the gas tank.
I had the same problem with my sled. Found gas in the oil container.
Turned out the vent line on top of the gas tank got pinched between the gas tank & frame when I re-installed the tank. Put about 4 gals. of gas in the tank and let it sit for a day or so. When you go to take the cap off the tank see if
you get a lot of back pressure I did.
Turned out the vent line on top of the gas tank got pinched between the gas tank & frame when I re-installed the tank. Put about 4 gals. of gas in the tank and let it sit for a day or so. When you go to take the cap off the tank see if
you get a lot of back pressure I did.
MSASRX
New member
There was a Yamaha bulletin on this exact issue - the main oil line coming from the oil pump goes directly to the fuel pump ( that's where it mixes w/the gas) and there is a "one-way check valve" on the oil line that some were failing and letting gas through the wrong way- and into the oil tanks.
I want to say it was from 2001-2003 somewhere in there. Ask a dealer to look it up maybe.
I want to say it was from 2001-2003 somewhere in there. Ask a dealer to look it up maybe.
shotym2
New member
I found same problem last night(97 600 SX twin). When I put it away last spring there was a little oil leaking from the pump. When I removed the fuel line from the pump, gas was pouring out of the line and when I pulled the oil supply line off the fluid was way too thin, diluted out with gas.
I pulled the fuel pump apart and the line from the oil pump and fuel inlet line from the tank enter into the same chamber. There is no check valve in the oil or fuel line. This means the fault is in the oil pump, and I will need a new one.
I pulled the fuel pump apart and the line from the oil pump and fuel inlet line from the tank enter into the same chamber. There is no check valve in the oil or fuel line. This means the fault is in the oil pump, and I will need a new one.
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2stroken
Member
shotym2 said:
What did you find on this?
shotym2
New member
We have not had enough snow to take it out and has been sitting in the trailer. I did top up the oil tank and it has not gone down, so it seems that the leak has been stopped. If we ever get enough snow to cover the rocks I will see what happens.2stroken said:
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