Gas in Crank case sight? (The hole where you see 2T)

[gregoryl]

Before doing a valve adjustment this weekend, I went to open the crank case sight hole (where you read 2T, 1T etc) and i smell a good deal of gas? What could be causing this? I dont have any smoke when firing up the bike, and i just ripped the carbs apart and everything was cleaned, and looked clean before i re-cleaned everything and pulled the idle screw caps and cleaned those. Any help would be great. I was thinking maybe a piston ring, but im having no smoke, and i did do a valve adjustment recently, and am having a little bit of excess noise still wtih the valves set at intake .004 and exhaust at .005. I was going to adjust them to .003 and .004 and noticed this smell so i wanted to get some answers before i started. Also, would Marvels Mystery Lube help the engine run smoother and maybe help seat the valves? I ran 89 to try to help seat the valves, and have rode maybe 40 miles.

Thanks, Luke

[csmith12]

Check the petcock operation.

[Klondike1020]

Originally Posted by csmith12

Check the petcock operation.

Sounds like your tank petcock/pump gadget is allowing fuel to go down into the carbs and find their way into the crank case.

make sure it is shutting off the fuel. Put an inline petcock if you have too.

but certainly change the oil before you run it anymore . might clear up the extra valve noises.

[gregoryl]

So i have put an inline fuel filter on. Seems like every once an a while the filter is not 100% full and then the tank will whine and then it will be completely full. Sometime its only half full. But when i turn on the bike and take the fuel line off, the petcock pours out gas, and when the bike it off and i pull the fuel line, no fuel is coming out? When cleaning the carbs, i also drained them into 2 Gatorade bottles, and both carbs had the same amount of gas in them.

[kxpower?]

Did you say whether your oil level (in the sight glass) has increased?

I might not sweat just a smell if the oil level has stayed the same. Gas is a bazillion times more volatile than oil so even a tiny amount in the oil should make it reek of gasoline.

[gregoryl]

I believe that the oil level has not changed, but the look of the oil seems to be a bit more light brown. Am i supposed to smell gas from that opening? What is that opening called anyway?

[kxpower?]

Originally Posted by gregoryl

I believe that the oil level has not changed, but the look of the oil seems to be a bit more light brown. Am i supposed to smell gas from that opening? What is that opening called anyway?

The oil filler? The bigger plastic threaded plug on the right side of the engine, toward the front?

No, I guess ideally you shouldn't ever smell gas anywhere in the crankcase. What I'm getting at is that it doesn't take a whole lot to flood the engine which would allow a little gas past the rings and into the crankcase, which would cause what you're experiencing. If the oil level had gone up noticeably I'd be looking at the needle valves and the petcock but there just isn't much volume of gas getting in there that I can tell.

If you want to play it safe I'd go ahead and change the oil and just keep tabs on the oil level going forward. See if the smell comes back too.

[cadd]

Even if the petcock is leaking, the floats in your carbs should prevent gas from overflowing.

Best way to check, if you're willing to cough up $25 bux is to get an oil analysis from Blackstone Labs. I did that with my 250 and got a clean bill of health. It still smells like gas sometimes though. But no traces of gas in there.

[gregoryl]

Thanks everyone! I am going to change the oil tonight. I adjusted the idle pilot screws as well and havent got a chance to check to see how the bike is performing since i blew the main fuse when i hooked the battery up backwards while the old lady was rushing me to leave. As for the place im talking about, its on the left side of the bike and is not the bigger (coin opened) part of the crank, its the smaller plug that when you turn the crank, you see "2T" or "1T". How do you get your oil tested? Thanks, Luke

[Ninjinsky]

If the vacuum diaphragm in the petcock is damaged or torn then the fuel has a direct run through the vacuum pipe and straight into the manifold.
This second route does not involve the float valve, it becomes just a pipe from the tank to the manifold

[kxpower?]

Originally Posted by Ninjinsky

If the vacuum diaphragm in the petcock is damaged or torn then the fuel has a direct run through the vacuum pipe and straight into the manifold.
This second route does not involve the float valve, it becomes just a pipe from the tank to the manifold

I was wondering about the vacuum diaphragm myself, I think it checks out:

Originally Posted by gregoryl

But when i turn on the bike and take the fuel line off, the petcock pours out gas, and when the bike it off and i pull the fuel line, no fuel is coming out?

[cadd]

Originally Posted by gregoryl

How do you get your oil tested? Thanks, Luke

Go to http://www.blackstone-labs.com and order a free test kit (which is essentially a plastic bottle). Do an oil change and fill up that bottle. Send in the bottle at USPS. Blackstone charges $25 for the analysis.

In the comment section of the form you fill out, tell them you suspect gas in the oil.

They'll keep an eye on the "flashpoint" for you and will comment on their findings.

[Ninjinsky]

Originally Posted by kxpower?

I was wondering about the vacuum diaphragm myself, I think it checks out:

Just pull the vac tube off the tap and see if any fuel drips out of the union. There should be none whatever vac side, it is a dry chamber.

[CZroe]

My petcock leaked and my oil smelled like gas a week after my oil change. It happened again when I changed it again. The smell was strong enough for anyone to notice when I changed my oil. I also had lots of top end noise. I stopped riding the bike because I feared the cam chain would give and I wasn't able to afford or do the work. Now I have a spare engine and a new petcock. There is evidence that a large number of these petcocka were bad/leaking and that they were redesigned internally but no recall and people keep saying that a leaking petcock should not be able to get past the carbs and piston rings to contaminate your oil, but I think it is easier than most believe.

[flitecontrol]

If the petcock leaks, and the float valve isn't sealing perfectly, gas will make its way to the cylinders and eventually the crankcase.

[CZroe]

Originally Posted by flitecontrol

If the petcock leaks, and the float valve isn't sealing perfectly, gas will make its way to the cylinders and eventually the crankcase.

I think the same applies to the float valves. Even if they seal fine, it wil make its way through to the cylinders and eventually the crank case (pressure changes and such).

[flitecontrol]

The VN750 has dual carbs fed through a vacuum activated petcock, similar to the Ninja. I never turned the petcock to off when parking, although I probably should, and never had gas in the oil. Both the petcock and at least one float valve have to fail for gas to get to the oil. Lots of gravity fed petcock bike owners don't turn the petcock to off when parking (again, they should) and don't develop gas in the oil because the float valve seals the gas in the carb.

[Ninjinsky]

Originally Posted by flitecontrol

The VN750 has dual carbs fed through a vacuum activated petcock, similar to the Ninja. I never turned the petcock to off when parking, although I probably should, and never had gas in the oil. Both the petcock and at least one float valve have to fail for gas to get to the oil. Lots of gravity fed petcock bike owners don't turn the petcock to off when parking (again, they should) and don't develop gas in the oil because the float valve seals the gas in the carb.

If the petcock diaphragm holes like mine did it leaks fuel down the vacuum line into the manifold not through the float chamber

[CZroe]

Originally Posted by flitecontrol

The VN750 has dual carbs fed through a vacuum activated petcock, similar to the Ninja. I never turned the petcock to off when parking, although I probably should, and never had gas in the oil. Both the petcock and at least one float valve have to fail for gas to get to the oil. Lots of gravity fed petcock bike owners don't turn the petcock to off when parking (again, they should) and don't develop gas in the oil because the float valve seals the gas in the carb.

Perhaps the difference is that our bikes have the tank whistle and pressure problems. Just yesterday I read about a member having a fuel filter that would be visibly only half full and then suddenly fill after the tank whine. The tank can either pressurize or form a vacuum.

Back when I had the faulty petcock my bike did smell like it was running extremely rich when it warmed up even though it was as lean as the day it left the factory. I'd bet it was excess gas forced into the cylinders and exhaust to blame.