Gas in the crankcase oil - again!

[Hoomgar]

I just did another carb rebuild. I noticed that I had gas in my crankcase after I did so I changed the oil. I re-jetted the carbs again yesterday and now I am getting gas in my crankcase again!?!?!?!!? :x

Why would that be happening all of a sudden? I would have thought that would be the petcock? Could the carbs be to blame if the petcock is still good or should I look at the petcock first? I am fairly certain the float needles and seats are good? If there a sure fire way to tell where the issue is?

[Buster Dog]

Have you cranked and ridden the bike since you rebuilt the carbs, or did you notice the gas in the oil before you cranked the engine? If the bike ran alright then it probably is the petcock. Does the petcock on your bike have a "prime" position? If it does and it's left in that position gas can overflow in the carbs and get into the engine oil through the intakes. If your petcock doesn't have a "prime" position then disconnect the fuel line from the petcock and see if fuel flows freely from the fuel outlet. If it does then you need to either replace the petcock or rebuild it.

[gspaul]

Hi Hoomgar.
If you float hieght's are not WAY out,and I do mean way out, it's two thing's ,your petcock is letting gas through when it should not, and one or more of your needle valves is staying open, either worn or dirty.
So two problem's, not to hard to fix ,so it will not have you off the road to long.

[earlfor]

Re: Gas in the crankcase oil - again!

I would guess the gas leak problem is coincidental and not caused by your carb work. I say this because even if you assembled your carbs and forgot to put the floats and jets in them, if the petcock is off and sealing, there would be no flow. If your float needle valves did leak, they could not leak more than what was in the float bowl if the petcock had the flow shut off.
I think its a certainty your petcock is leaking. The float needle valves may be seeping too, but the petcock for sure.

(yeah, I know Keith and I went round and round about the lean angle of a bike on the sidestand and the fact/possibility that there can be seepage with a good petcock.) If so, I believe it will be very minimal. (I do soooo
enjoy making Keith jump up and down and pull his hair though :-) :-) :-) )

Earl

I just did another carb rebuild. I noticed that I had gas in my crankcase after I did so I changed the oil. I re-jetted the carbs again yesterday and now I am getting gas in my crankcase again!?!?!?!!? :x

Why would that be happening all of a sudden? I would have thought that would be the petcock? Could the carbs be to blame if the petcock is still good or should I look at the petcock first? I am fairly certain the float needles and seats are good? If there a sure fire way to tell where the issue is?

[Hoomgar]

Well I just wanted to hear someone else say it. Thanx Earl, and you other guys. I think I need to rebuild the petcock. BTW, I very rarely park on the sidestand. Almost never. Bike hasn't been on it in weeks.

Now, where did I put that dern petcock rebuild kit I bought?

[retrex]

Gas in crankcase

Hoomgar, I had the same problem on my 81GS11. It turned out to be the petcock's vacuum diaphram. Filled my crankcase with so much gas that the engine was in hydrolic lock. It would not even crank. Replaced the entire petcock as I was out on the road. One other thing that comes to mind in veiw of what earlfor said,

If your float needle valves did leak, they could not leak more than what was in the float bowl if the petcock had the flow shut off.
I think its a certainty your petcock is leaking. The float needle valves may be seeping too, but the petcock for sure.

are you sure all your floats still float. I had one that became gas logged and would not seat the needle. Just a thought.

[Hoomgar]

Re: Gas in crankcase

are you sure all your floats still float. I had one that became gas logged and would not seat the needle. Just a thought.

Yes, these floats sat dry for a long time until last week.

[retrex]

Re: Gas in crankcase

are you sure all your floats still float. I had one that became gas logged and would not seat the needle. Just a thought.

Yes, these floats sat dry for a long time until last week.

Floats can become porous over time. They can absorb gas and become less boyant. The point I was trying to get across is that when I clean carbs I drop the floats into gas to observe if they sit high, low or sink in the gas. Any that don't cut the mustard get chucked. What earlfor was saying about the needles seeping brought this to mind. Just thought that I would throw it out there for you to consider.

[Hoomgar]

Re: Gas in crankcase

are you sure all your floats still float. I had one that became gas logged and would not seat the needle. Just a thought.

Yes, these floats sat dry for a long time until last week.

Floats can become porous over time. They can absorb gas and become less boyant. The point I was trying to get across is that when I clean carbs I drop the floats into gas to observe if they sit high, low or sink in the gas. Any that don't cut the mustard get chucked. What earlfor was saying about the needles seeping brought this to mind. Just thought that I would throw it out there for you to consider.

Yeah I know. It is a good point. I know these are those composite type floats too. I do know the petcock was weepy a bit so I'll replace it regardless but I am going to check the floats next time I have the bowls off too. Especially if the petcock rebuild doesn't fix it

I like the floats in my smoothbores. Soldered brass baby

[earlfor]

Re: Gas in crankcase

If you rebuild your petcock with a kit and by chance still get a weep, 99 times out of 100, the problem will be the "O" ring on the plunger that sits next to the diaphram is one that was manufactured undersize. The fix is Suzi dealer and a 25 cent "O" ring the right size. :-)

Earl

[quote="Hoomgar"]
I do know the petcock was weepy a bit so I'll replace it regardless but I am going to check the floats next time I have the bowls off too. Especially if the petcock rebuild doesn't fix it

[duaneage]

Next time you have the floats off drop them in a baby food jar of gas and let them sit for a while. Make sure they all "float" at the same height or they will not be bouyant enough to hold the needle valves shut.

[KEITH KRAUSE]

If it's the petcock, just attach a longer fuel tube into a jar and see if fuel goes in the jar overnight or the normal amount of time the bike sits between runs. Do the same for the vacuum tube if you think it may be leaking from there.
If it's the floats or float valve(s), you can check for debris interfering with the valve. Float problems as stated earlier. It doesn't take much wear near the valve tip to cause a leak. Hopefully, you didn't mix the valves and their seats up. They wear as a unit and must be kept together. Be sure you replaced the fiber (stock) or metal float valve seat gasket. Be sure things are tight. Another way to locate the leak after sitting awhile, is to take the filter off each carb and wipe the bottom of the carb throat/intake with your finger. If you see/feel one wet, there's your leaker.
If after making sure the petcock is good and you still have the problem, then you know it's the floats or valves. After several shut downs, the fuel left in the fuel line and carb passages can amount to quite a bit of gas in the crank. Fuel can still drop down by gravity even with a good petcock. It's just a fact. The bike parked on the sidestand can cause the fuel to drop quicker, but it will still do it on the centerstand too. If the fuel line was going STRAIGHT down from the petcock, I'd have to agree that the suction would keep the fuel in the line. But the fuel line doesn't go straight down, it goes almost horizontal and bends down to the carb. This is all you need to break the suction and the fuel will drop. Test for yourself sometime.
Bottom line is, if the valves are sealing correctly, a leaking petcock can't get past them unless the petcock is leaking into the vacuum tube and entering carb #3 and then straight to the crank.

[Hoomgar]

Bottom line is, if the valves are sealing correctly, a leaking petcock can't get past them unless the petcock is leaking into the vacuum tube and entering carb #3 and then straight to the crank.

This is my suspicion at this point. I'd bet on it. Keith, do you run pingle shut of valves or do you prefer the stock vacuum setup?

[KEITH KRAUSE]

Bottom line is, if the valves are sealing correctly, a leaking petcock can't get past them unless the petcock is leaking into the vacuum tube and entering carb #3 and then straight to the crank.

This is my suspicion at this point. I'd bet on it. Keith, do you run pingle shut of valves or do you prefer the stock vacuum setup?

I love my little Pingel! I take it with me where ever I go!
Seriously, it's a good upgrade.

[Hoomgar]

Bottom line is, if the valves are sealing correctly, a leaking petcock can't get past them unless the petcock is leaking into the vacuum tube and entering carb #3 and then straight to the crank.

This is my suspicion at this point. I'd bet on it. Keith, do you run pingle shut of valves or do you prefer the stock vacuum setup?

I love my little Pingel! I take it with me where ever I go!
Seriously, it's a good upgrade.

And I have been converted, finally. It is going to happen. I have 15 miles on the oil in that engine and it is filled with gas! Again! I can't deal with this.

I am going to have to learn to turn fuel on and off now.

Thanks again.