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Gas in the oil

  • Thread starter Thread starter SeanMora77
  • Start date Start date
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SeanMora77

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Im running through the wiring harness trying to find a reason that 1 and 4 are getting no spark. Im on the floor of my garage with my light shining under the bike, tracing wires from the ignitor box when i notice the oil level is way high through the sight glass. I unscrew the oil cap and smell gasoline in the oil. What is causing gas to get in there?:mad: This bike is getting to be a real nightmare.
 
Faulty petcock, stuck float in a carb...there will be more suggestions shortly.
Don't use that oil any more.
 
SeanMora77 said:
Im running through the wiring harness trying to find a reason that 1 and 4 are getting no spark. Im on the floor of my garage with my light shining under the bike, tracing wires from the ignitor box when i notice the oil level is way high through the sight glass. I unscrew the oil cap and smell gasoline in the oil. What is causing gas to get in there?:mad: This bike is getting to be a real nightmare.
Click to expand...
There is really only one reason and way for gas to get in the oil, and I'm afraid that it's not good. How much have you been running the bike?

Do you have a vacuum actuated petcock or a manual one?

When the petcock fails, or you leave the petcock on PRIME, gas constantly flows down the fuel line. The float needles SHOULD do their job and seat, to stop fuel flow, but problems with those not seating will show up as gas in the oil. Basically, gas flows up the intake (engine side) side of the carbs and you end up flooding the engine as the carbs tip towards the cylinders. The gas is thin enough that eventually it works it's way past the rings and into the crankcase.

Is the bike level? Even small tilts of the bike to the right will make the level appear higher (guilty of that myself)

Plenty of threads on troubleshooting it, but you are looking at an oil and filter change at minimum, and if you have just been leaving the petcock on PRIME. The worst case scenario would be replacing the petcock, oil and filter change, and new needles and o-rings. There's a recent and good thread started by MisterCinders where he's been having gas in oil problems.

EDIT- here's the thread

http://www.thegsresources.com/_forum/showthread.php?t=192476

First off, find out if your petcock is working properly.

Have you done a full cleaning and inspection of the carbs yet?
 
Last edited:
Thanks for the shout out BigD.

First off DO NOT START THAT BIKE UNTIL YOU CHANGE THE OIL AND FILTER.

As to what puts fuel into the oil, you need to trace through the fuel supply system for something that fails to regulate fuel.

Start with the petcock. Is it leaking fuel through the vacuum line? That line goes into your carb without a valve, so if fuel finds its way there, it will keep flowing, overtake the bowl, run into the intake, etc. Pull the tank and line and set the tap to ON. If no fuel comes through the line, apply some light suction to the vacuum line to see if that causes gas to flow through the fuel line (it should). See if gas also went through the vacuum line (it should not). If that checks out, do the tkent siphon test and run your fuel line down into a small container like a jar or small bucket. You can do this with the tank on the bike and the container on the ground, if you have a couple feet of fuel line. Switch to PRI until you have enough fuel to submerge the end of the fuel line and mark the fuel level in the container. Then return the tap to ON and let sit for a few hours. When you come back, check the level in that container to see if there is a small leak in the petcock.

If the petcock checks out (mine did), then you need to check the float valves and seats and the float levels. Pull the carb bowls and check the float levels. If they are too low (i.e., too high when the rack is on the bike), then you have too much fuel in the bowls. That usually runs off in the overflow tubes though, so make sure they are not clogged. You should also adjust the float levels to not squander gas into the overflow tubes.

Now check the seats, needles and washers. Pull the floats and the needle/seat assemblies. Clean them out and then do a blow test by holding the needle in the seat and gently blowing through them. As you lightly press the needle into the seat, you should not be able to blow through it. Otherwise, you'll need to change out the needles and/or seats for better parts.

If that checks out, reassemble the needles, seats and floats. Adjust the float levels to spec. Now install the bowl gaskets and make sure the floats are not snagged by anything. Part of my problem was that the gaskets were a bit wide and would rub against the float, preventing it from closing.

Next, flip the rack without bowls and run some gas through them over a big pan (like an oil change pan). You should see gas flow out of the needle valve until you lift the float gently. If gas flows or dribbles in when the float is up, you have a bad washer under that seat. I ran into this on one of my carbs that continued to leak fuel.

Finally, another source of fuel is the choke circuit. Make sure that each is closing properly when the choke is off. Clean the passage and choke assemble and check that it moves freely up and down.

HTH
 
The petcock is vacuum actuated, and the bike is sitting on the centerstand in my garage so I'm assuming that would be level. I just had everything torn apart a few days ago and I took the petcock apart to find out why it was so hard to turn and discovered it was the o ring in the selector lever. I replaced it and re assembled it. The diaphragm seemed fine, no holes or badly worn spots from what I could see... I'm thinking this may be a carb issue. I recently cleaned the Carbs and re-adjusted the float heights. If you are looking at the carb with the float bowl off from the profile there is a rounded part and then a flat part on the top of the actual float. I made my adjustments to spec using the top of the round portion of the float as per the mikuni carb rebuild tutorial on basscliffs site. This adjustment required quite a bit of (tweaking) of the tab to get them to the proper height. Just yesterday when I re assembled everything I noticed a small amount of fuel leaking from the airbox. I thought that it may have been from a stuck spring on the float needle and it stopped as soon as I ran the bike. I am at a loss here, where should I start?
 
All the carbs can do is let it run rich when it's running, if fuel is getting into the oil it is a petcock issue.
With a good petcock there will be no fuel for the carbs to leak into the oil.
 
Very likely the petcock- just replacing an o-ring might not have been an improvement. Disconnect both gas line and vacuum line from petcock (leave lever in "on" or 'Res" spot), anything flowing? Nothing should be, then put clear vinyl tubing on petcock vac fitting, suck on it, fuel should flow, but no gas should show up in vinyl tubing. stop sucking fuel should cease flowing fairly quick.
 
Thank you all for the help. I don't think Ill be able to start tearing things apart until tomorrow or very late this evening. On the upshot, I only rode the bike for maybe two miles total yesterday. No smoke from the exhaust to speak of and no startling noises. If the petcock is not supposed to leak fuel when the main line is disconnected than my petcock must be shot. The vacuum line of the petcock has never leaked any fuel at all but like I said, if i remove the tank and the fuel line from the petcock fuel runs out in a steady stream. As I understand the diaphragm should colse when no vacuum is applied thus stopping any fuel from flowing out? As my father in law and I were trying to diagnose an issue with the one and four cylinders not firing I noticed that i had the petcock set to prime where it must have been for at least an hour, dont know if that has any relevance at all, just wanted to give as much detail as possible. Thanks again evryone, your insight is very much appreciated.
 
PRIME is the gravity setting. If you turn the tap to PRIME, then it should allow fuel to flow through the fuel line regardless of vacuum and will leak when you disconnect the fuel line.

If your petcock is releasing fuel without vacuum while in the ON position, that's not good. These petcocks have no OFF position like gravity fed models, so every time you park the bike, it is letting fuel go down the line. Once that pressure overwhelms the needles, it floods.
 
Thanks for the help folks. I drained the oil and removed the filter. Gas tank is setting on the floor of my garage with a stopper in the petcock hole until I can either repair the one I have or buy a new one. Another setback but I'm steadily closing in on having a healthy running bike. Thanks again
 
Do Not Bother with trying to rebuild the Petcock. Get a new one and you will sleep much better! Ask me how I know :)

Good luck

Terry WBL
 
Have not purchased the petcock yet, but definitely going to. Bike is in pieces yet again. Found rust in the gas tank, again. I'm just going to bite the bullet and por15 the tank. Got an ever growing list of parts I need to get before I start her up again.
 
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