Gas Leaking into Oil

crobwolfpack · July 11, 2012, 04:33:01 PM

I feel like all of my posts have been asking for help with the fixer-upper I got, but you guys have been on point with the help and I really appreciate it!!!

So my final issue is that my dipstick smells like fuel. Aside from changing the oil and oil filter, what should I be looking for as the cause? I'm thinking my float levels in the carb may be off but I'm not positive.

Also, the bike only runs with the petcock set to "Prime", not "run". Taking it apart tomorrow to get a close up, but what should I be looking for in specific within the petcock?

Thanks so much for all the help guys, definitely been a lifesaver!

mister · July 11, 2012, 04:41:30 PM

Before you take apart the petcock and look for some mysterious thing... does it do this with a full tank as well?

If so, if it runs in Prime and Res but not on, most likely the vacuum diaphragm is kaput. Could also be a totally blocked fuel line coming from On, but most likely bad diaphragm. Assuming you do NOT have an additional fuel filter coming from the petcock, as they can mess up your fuel flow too.

Michael

crobwolfpack · July 11, 2012, 05:07:39 PM

Not sure if it does it with a full fuel tank, I'll certainly check that though. If it is the vacuum diaphragm, is that something that can be fixed/cleaned or will I need to replace the petcock?

mister · July 11, 2012, 05:28:07 PM

Quote from: crobwolfpack on July 11, 2012, 05:07:39 PM
Not sure if it does it with a full fuel tank, I'll certainly check that though. If it is the vacuum diaphragm, is that something that can be fixed/cleaned or will I need to replace the petcock?

I mention full tank cause the tank on the GS is deceptive and can look full when it is really not and will only run on reserve. Your only fuel issue might be that common mistake for new GS owners.

This diagram from the wiki shows how the diaphragm works...

If the diaphragm has a hole in it or rip you cannot Fix it. But before getting into solutions to that, see if it does it with a full tank and check your fuel line for pinches which often happens if you've lifted the tank and played around.

Michael

adidasguy · July 11, 2012, 05:32:50 PM

#5055

Often the vacuum line to the petcock is not connected correctly or is pinched. PRIME comes off the reserve fuel line. If it runs in reserve, your main line is pinched or clogged. If only in prime, you may have a disconnected vacuum line or it is connected to the wrong place or the line has a crack in it.

It could be stuck if the bike has been sitting a long time. One way to un-stick it is to connect a hose to the fuel out. BLOW HARD into it. The force of air will often pop it free. Another way is to suck hard on the vacuum input. The carbs have very little vacuum - your lungs have much more.

crobwolfpack · July 11, 2012, 05:57:29 PM

Cool, I'll definitely check into that. If the line is pinched or something, could the reason the gas is leaking into the oil just be an overload of fuel given that it's been running on prime?

RossLH · July 11, 2012, 06:05:16 PM

Noob question about the vacuum line: where exactly would it go on a '93 GS500 carb? I took the carbs off and negligently did not pay attention to where everything was. I think I have it in the right place (nipple on the left carb just behind the choke lever), but I just want to double check.

adidasguy · July 11, 2012, 06:24:15 PM

#5056

Quote from: RossLH on July 11, 2012, 06:05:16 PM
Noob question about the vacuum line: where exactly would it go on a '93 GS500 carb? I took the carbs off and negligently did not pay attention to where everything was. I think I have it in the right place (nipple on the left carb just behind the choke lever), but I just want to double check.

Yep - that's where it goes on the 89-00 carbs.

If your floats are stuck, leaving on prime will allow excess gas to overflow the carbs. Likewise, stuck floats could cause the carbs to always overflow when running and idling as gas flows in faster than you're using it --- but that depends on how stuck open the floats are. Floats control the flow of gas - opening and closing as the carb bowls need gas. If the floats are OK, even leaving on prime won't cause a problem as the floats will stop the flow of fuel.

The difference between prime and on/res is prime forces the petcock open in the absence of a vacuum. Usually that position is for re-filling the carbs after you emptied them.

RossLH · July 11, 2012, 07:06:32 PM

Quote from: adidasguy on July 11, 2012, 06:24:15 PMYep - that's where it goes on the 89-00 carbs.

Excellent, thank you sir! Hopefully I'll get this thing up and running soon.

crobwolfpack · July 17, 2012, 04:01:46 PM

So I looked at everything and I'm fairly sure my floats are out of position and the bike is a 93 so the valve seat may be worn. I got a carb rebuild kit so hopefully once I do that I'll be good to go!

crobwolfpack · July 30, 2012, 10:20:39 PM

Made a mistake and only got 1 new valve seat and needle (used to single carb, forgot it was a duel carb), but after taking apart the carb and taking out both seats, only the right O-ring looks dirty. So, I'm just gonna replace that valve seat and needle... thoughts? Also, my floats were off so I set those correctly.

Quick question, when putting the valve seats in is it a horrible idea to use some kind of gas resistant sealant to ensure it is snug and prevent gas leaking past???

Thanks!

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Gas Leaking into Oil