Gas filled the crankcase

[Scott91370]

Here's a new one for me.

It's not a street bike but a 4 wheeler. 2004 Yamaha Big Bear.
Last rode it Saturday night. Was in the garage last night and everything was good visually. Smelled something but I had used brake cleaner in there a couple of days ago so didn't think much of it.
Went out today and there was a puddle on the floor. Smelled like gas. Look in the tank - almost empty. Gas was seeping out of the left side of the engine where the pull start is mounted.
Checked the fuel shut off since it is carb'd and it is in the off position.
Since the tank was full I wonderd where it went. Rolled it outside and removed the oil fill/check cap and for 45 seconds it poured out.

Question is, since the valve is turned to close (and it worked a couple weeks ago because I forgot to turn it on and the bike ran for a bit then died) what could cause the fuel to do this?
My only thought is, float sticking open. And since it's gravity fed the most likely place is for it to go down until the tank is empty.

Any thoughts, ideas or critisism is welcome!!

 

[DFW_Warrior]

Sounds like a stuck float and then depending on the set up, it might have filled the air box up to the point where the crank vent ties in and down it went.

Perhaps the petcock and float are dirty and leaking?

 

[Scott91370]

I checked the on/off valve ad it is not leaking.

The airbox is lower than the carb and it did have some gas in the bottom so you may be right. The carb is fairly new but if there was dirt in the gas and it found its way to the needle valve or the float got stuck you're right, it would do this.

Thanks for your insight and I'll be tearing into this soon - probably Monday since bird season starts and I won't be with th 4 wheeler for a few days.

 

[Jeff S]

Been there, not fun to clean out.

There's gotta be a petcock leak - that's the only line from the tank to carb to cylinder, past the rings, and into the case. Check the float valves also (not just the floats).

You're doing an oil change now, I assume?

 

[DFW_Warrior]

I checked the on/off valve ad it is not leaking.

There's gotta be a petcock leak - that's the only line from the tank to carb to cylinder, past the rings, and into the case.

I agree with @Jeff S on this one. There is only one way for gas to get from the tank into the carb and then into the crankcase, and that is through the petcock. There either has to be something up with it or it wasn't turned off all the way.

As for an oil change, since gas is a REALLY good solvent, I would not only do an oil change, but I would run the motor on the oil change for 5 minutes or so and then dump that oil and go with another batch of fresh. It is cheap insurance to get as much gas out of there as possible.

 

[HiSPL]

If its a vaccuum petcock you could have a hole in the diaphragm which lets the gas go into the vaccuum line and down the intake.

Been there before.


Look at it this way. The bottom end is sparkly clean now!

 

[Windmill]

I have a motor on a bike that had miky oil. I did this this week at the advise of the best auto mechanic I know. I drained it then rinsed filter added two quarts of MMO then let it drip out slow through loose plug. Next new oil and filter run till warm then repeat oil change. This is what he told me to do not advising anyone else to do it. We will see when I get the chip key. It seems clean as a hounds tooth now . Hope the head gasket is good and water pump seal. We will see .

 

[Scott91370]

Been there, not fun to clean out.

There's gotta be a petcock leak - that's the only line from the tank to carb to cylinder, past the rings, and into the case. Check the float valves also (not just the floats).

You're doing an oil change now, I assume?

I agree with @Jeff S on this one. There is only one way for gas to get from the tank into the carb and then into the crankcase, and that is through the petcock. There either has to be something up with it or it wasn't turned off all the way.

As for an oil change, since gas is a REALLY good solvent, I would not only do an oil change, but I would run the motor on the oil change for 5 minutes or so and then dump that oil and go with another batch of fresh. It is cheap insurance to get as much gas out of there as possible.

I pulled the line that goes from the petcock to the carb and nothing came out. Let it sit for about 5 mins, unhooked, while I cleaned a few other things and nothing. Of course, the fuel level could have been so low that there wasn't anything to leak. I will put some more gas in and test it.

Oil change? BAH!! No, of course. I've actually got the oil drain open right nowand will leave it open until I am ready to change the filter and refill. And as DFW_Warrior stated, I will run it for a short bit then do another fluid & filter change - maybe twice since it only uses 3 quarts it's way cheaper to be safe than sorry.

 

[Scott91370]

If its a vaccuum petcock you could have a hole in the diaphragm which lets the gas go into the vaccuum line and down the intake.

Been there before.


Look at it this way. The bottom end is sparkly clean now!

How do I tell if it is a vacuum style?


I'd like to open it up and see just how clean it is!!

 

[Scott91370]

Quick still shot since I can't upload the entire video:

 

[HiSPL]

How do I tell if it is a vacuum style?


I'd like to open it up and see just how clean it is!!

It’ll have a vacuum hose routed to the intake boot area. Or maybe to the back side of the carb.

Basically a fuel hose to the carb, and a vacuum hose to somewhere behind the carb. Two hoses total.

 

[Windmill]

I will use some cheap oil I have to run and flush then new filter and the synthetic good stuff. I try to put gas cocks on mowers and bikes if possible. My XR650 has a Clarke tank and a manual valve.
I normally run. oil from the earth
Please no oil thread

 

[Scott91370]

I will use some cheap oil I have to run and flush then new filter and the synthetic good stuff. I try to put gas cocks on mowers and bikes if possible. My XR650 has a Clarke tank and a manual valve.
I normally run. oil from the earth
Please no oil thread

I plan on using the cheapest oil for 2 fillups. Let it run for maybe 5 mins on the first change then 10-15 on the second one. I'll capture some of the oil in a clear container on the second and check it for seperation. If it looks good I'll put in the best oil I can find - from an oil thread where everyone agrees.

 

[dash1]

I had this happen with a bike I restored for a friend of a friend. The vacuum petcock decided to spring a leak while it sat for 6 years and gas filled the crankcase and ate the gaskets. Most of the oil leaked out and it had tons of varnish everywhere.

I did three back to back oil changes with cheap rotella and it was running good but the gaskets were shot and it wasn’t worth splitting the engine to fix the slow oil leak. Last I heard it got put away in storage again.

 

[julimike54]

You may want to make sure the gas cap will vent. As hot as it has been the gas may have expanded and pushed its way through the petcock and float valves. Then the siphon principle may have worked its way into the equation...

 

[Scott91370]

You may want to make sure the gas cap will vent. As hot as it has been the gas may have expanded and pushed its way through the petcock and float valves. Then the siphon principle may have worked its way into the equation...

Checked that already and it does. Good thining though!

 

[Boulder Ed]

I agree with @Jeff S on this one. There is only one way for gas to get from the tank into the carb and then into the crankcase, and that is through the petcock. There either has to be something up with it or it wasn't turned off all the way.

As for an oil change, since gas is a REALLY good solvent, I would not only do an oil change, but I would run the motor on the oil change for 5 minutes or so and then dump that oil and go with another batch of fresh. It is cheap insurance to get as much gas out of there as possible.

I did the dump and repeat process when I accidentally dumped tranny fluid in my engine once Summer drinking and wrenching does not always work out in Texas, due to the heat.

 

[Windmill]

I did the dump and repeat process when I accidentally dumped tranny fluid in my engine once Summer drinking and wrenching does not always work out in Texas, due to the heat.

Never worked in the winter for me either
I knew a guy that was rebuilding an old Harley 20 years ago with a beer in one hand and a cigarette in the other. If he is still alive I bet he is still working on the rebuild. I haven't seen him in ten years.

 

[Scott91370]

Susicion #1 confirmed - Fuel petcock not fully closing when in closed position. It appears to be the original and the screen was only attahed in a few small spots so if there was any deris in the tank I'm sure it got past it. Which will probably lead me to suspicion #2 - debris in the needle/seat/float keeping it open.

Biggest problem now is whoever did the last oil change tightened the **** outta the plug. I've going to have to clean the area ad use some heat. The bolt head on the plug is already a little rounded so I trhink I'm going to also have to cut a groove and use a big ol' screw driver.

Parts on order: 4 oil filter, 1 drain plug, one fuel petcock.

 

[Jeff S]

Heat and gas filling the crank case = make sure this is on video

 

[Windmill]

use a heat gun

 

[HiSPL]

use a heat gun

Also an impact gun is your friend along with the heat. The shock of the impact often is better and gentler than rounding it off with a big cheater bar. If you’re already considering things like slotting the bolt, vice grips, etc. I try the impact and a six-point socket first.

 

[Scott91370]

Heat and gas filling the crank case = make sure this is on video

Case has been open for 4 days so it's only fumes - the flamable part ya know. But if the case was still full, it's be safer. Notice I didn't say safe.

Also an impact gun is your friend along with the heat. The shock of the impact often is better and gentler than rounding it off with a big cheater bar. If you’re already considering things like slotting the bolt, vice grips, etc. I try the impact and a six-point socket first.

Impact wouldn't work and I only use 6pt. The corners were rounded and nothing would bite.

I did slot the bolt but it was so soft it started to chip away.
Ended up grinding a notch in the edge and using a flathead and hammer. It definately had way mpore than the 23lb/ft it's supposed to.

All new parts are installed, just need to run the fresh oil though. I got enough oil and filters to do 3 flushes. Fisure I'd start with a 10 minute run, at idle, for the first then 20 and 30.

Cleaned out the crab and it looked like a sandbox. I'm guessing the torn screen on the petcock assembly was the cause of letting the dirt through. I'm also going to add an inline filter.

 

[HiSPL]

I did slot the bolt but it was so soft it started to chip away.
Ended up grinding a notch in the edge and using a flathead and hammer. It definately had way mpore than the 23lb/ft it's supposed to.

Sounds like dissimilar metlal corrosion to me. Steel bolt into the aluminum case and it'll get stuck good eventually. Throw some anti-seize on it.

 

[Scott91370]

Sounds like dissimilar metlal corrosion to me. Steel bolt into the aluminum case and it'll get stuck good eventually. Throw some anti-seize on it.

Both are aluminum but after rmoving the filter this afternoon I'm not so sure the plug has ever been removed. While it only has 1400 miles (or maybe 101400) the yuck in the filter housing was dark. The original oil that drained wasn't too bad looking so who knows.
Anti-sieze isn't a bad idea!!

These are the kinds of things that happen when you buy a used anything, I did get a good deal on it so as log as it runs a few years I won't be too mad.