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ripntear

Gas in oil causes???

18 posts in this topic

My oil is diluted with gas. I put around 8 hours between changes or 2 rides, and the last 4-5 changes I have noticed a considerable amount of gas in the oil. What are some things to check for?

I do not roll the throttle when loading/unloading the bike.

The petcock is not leaking when off.

The bike is not running rich.

I have not noticed any gas overflow (stuck float).

Thanks!

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If gas is getting in your oil its probably passing through the rings. We have the same problem on our CBR600 race bike.

compression test might tell you if its leaking

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It is definitely gas. No water.

If it is valve seats, can they be replaced without special tools? I was looking in the manual and it's hard to tell. Should I go ahead and replace the valves and springs while I'm doing the seats? What else should be done if you are this far into the top end?

As far as the rings go, I did not see the recommended compression level in the manual. Hopefully one of you have this spec.

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Doubt it’s the rings... When the bike is running it is hot enough to burn the gas off that is in the oil.

I would put money on it being a Carb related problem like a stuck needle and seat. If the needle and seat are stuck open (even a little) the fuel would start to over full the bowl of the card and run into the cylinder then past the rings into the oil....

With this theory the bike should be a bit of a bitch to start as it would be flooded quite a bit?

I would whip the bowl off the carb while its in place and hold the float up and turn on the gas tap and see if there is a good seat between needle and seat. Its a quick and easy test to eliminate that possibility.

Let us know what you find.

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It's not the valves; there's no way for things leaking by the valves to get into the oil. What temps are you riding in? Does the bike get up to normal temp during a ride? If yes, I would expect it to be hot enough to steam off the gas and my guess would be a very slow leak in your petcock when the bike is off. If no, then it's very possible that the bas is building up while it's running and the temp just isn't high enough to steam it off (is your breather hose restricted in any way?). This happens with outboard boat motor 4-strokes all the time when people idle around all day. They run much cooler than the average motor and don't steam off the gas at very slow speeds. Try this; change the oil immediately before a ride. Check it when you put the bike away, then check it again next time you take it out. If there was no gas when you put it away, but gas when you took it back out then you're definitely getting the gas in while it's sitting. You can also keep a very close eye on the gas tank level while it sits. Hope this helps, let us know what you find!

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The temp has been high 80-90s'. I have pulled the fuel line from the petcock and watched to see if it had a slow leak. Nope, dry as a bone. I don't do much putting around, so I can't see that being my problem.

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Needle and seat... its got to be...

While the bike is not being used at full taps the petcock is still turned on and the fuel is by passing the needle and seat into the oil... Its impossible for these bikes to use as much fuel as the petcock delivers, there for the needle and seat stops it from over filling... it could be a piece of dirt there stopping it from sealing properly...

Pull the bowl of the carb off and hold the float up (closed) and see if there is a leak...

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Needle and seat... its got to be...

While the bike is not being used at full taps the petcock is still turned on and the fuel is by passing the needle and seat into the oil... Its impossible for these bikes to use as much fuel as the petcock delivers, there for the needle and seat stops it from over filling... it could be a piece of dirt there stopping it from sealing properly...

Pull the bowl of the carb off and hold the float up (closed) and see if there is a leak...

I will check it out. I hope it's something as simple as this!

I'll let ya know what I find.

Thanks!

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Well, took the carb off and checked the float. It shuts off properly and appears to be adjusted fine.

Also checked the needle valve and valve seat. They were clean and seemed to be working properly.

All vents are clear and working properly.

I left the fuel line disconnected to make sure the petcock is not leaking and have seen no sign of gas for well over an hour.

If I rule out the carb as the problem, what else could it be?

I'm riding this weekend and will change the oil after I get back to check it.

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I would say it is your rings. Do a leak down test not just a compression test. Time how long it takes for the compression to go away. If it goes away really fast I would say the rings are cooked. Just my 2 cents.

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Could be the rings are worn and you're getting a pile of blow-by, as mentioned above. Unusual that you would get gas build up at normal riding temps though. Perhaps not impossible, but really unusual, especially seeing how much ventilation these motors get through the breather. Let us know whatever you find.

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My bike runs strong. If I had to guess, it has less than 100 hrs on it. It has always been maintained properly. I guess I'll look for a leak down tester and see what I come up with. Any brand recommendations? I hate to go at things in a shotgun approach but it sounds like it's more of a process of elimination which I have already started.

Dose anyone know what percentage of leak is within tolerance? Also, how will I be able to determine if it's the rings and not the valves thats leaking?

Any ideas or suggestions will be greatly appreciated.

Thanks!

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Get a difference in pressure type leakdown tester (two gages) not a percentage type, as they are more accurate.

You can tell whats leaking by listening in the exhaust for air, in the airbox, and in the cases for leakage past the rings.

I would suspect the needle and seat, but you said you checked it.

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i've noticed that (especially if your running a little rich) some oils retain the gasoline smell more than others :banghead: i went through the same thing with my WR

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i've noticed that (especially if your running a little rich) some oils retain the gasoline smell more than others :banghead: i went through the same thing with my WR

Did you find a fix or just live with it? I'm wondering if the AP length squirt would contribute to this especially in tight stuff where you are on/off the throttle constantly?

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