Fuel in Vacuum Ports

I'm getting fuel in places I don't think I should. First, a little history. The bike sat for a long time resulting in trash in the tank, but not much rust. So, I cleaned it out and used an inline fuel filter. After getting the bike road worthy, I noticed a fuel leak that was worse on the side stand vs the center stand, mostly from the #2 carb. I also noticed that the oil level was increasing and the oil was getting dark really quick. I concluded that it was the float bowl gaskets, and replaced them. The problem seemed to be fixed, but a couple of weeks later, the leak was back, again mostly on the #2 carb. And the oil level was still increasing and the oil was getting dark too quickly. Suspecting that fuel is getting the crankcase somehow, I checked everywhere I could think of for leaks. Yeah, the carbs were leaking, but I would think that if the crankcase gaskets can keep oil in, they should be able to keep fuel out. So I checked the vacuum ports (where you sync the carbs), and every time after I run it, I can pop off the caps and get a couple of drops of fuel out of them. Is this right? This doesn't seem to be to me. I took off the carbs again and checked the bowls, and they were full of dirt, so that could have been the cause of the leaks. I cleaned them out (again), cleaned off the float needles, and replaced the fuel filter. The filter was an old one and I probably shouldn't have used it. I changed the oil again and took it for a ride (about 1hr). I can't tell if the oil level has changed, but the color of the oil hasn't changed. I'm still getting a couple of drops of fuel in the vacuum ports. Is this right?

You'll always get a little gas out of those ports when you remove the caps.

RonKZ650, thanks. I was hoping that was the case. I'm getting tired of pulling the carbs. But at least I AM getting faster at it.

bemoore wrote:

RonKZ650, thanks. I was hoping that was the case. I'm getting tired of pulling the carbs. But at least I AM getting faster at it.

Amen. The first time I did it, it took me almost an hour to get them back on. The other night, I came in from the garage and proudly announced to my wife that I just installed my carbs in about 5 minutes.

She was VERY impressed. :whistle:

bemoore wrote:

...oil level was increasing and the oil was getting dark really quick...a couple of weeks later...oil was getting dark too quickly. Suspecting that fuel is getting the crankcase somehow, I checked everywhere I could think of for leaks. Yeah, the carbs were leaking, but I would think that if the crankcase gaskets can keep oil in, they should be able to keep fuel out...checked the bowls, and they were full of dirt, so that could have been the cause of the leaks. I cleaned them out (again), cleaned off the float needles, and replaced the fuel filter....can't tell if the oil level has changed, but the color of the oil hasn't changed....

Crankcase gaskets cannot keep fuel out.

If overflow tube inside float bowl is obstructed (or there's no overflow such as with smoothbores), and the float needle/seat closure is not perfect, and the petcock is left open or not properly closing -- under such circumstances, fuel level may rise in the float bowl and on up into the carb throat to flow rearward into the air box (or into the pods) and flow forward into the combustion chamber down around the pistons and into the crankcase. Where the crankcase vents through a hose to the airbox, fuel collecting in the airbox drains down through the crankcase vent into the crankcase. So where using an airbox with smoothbores, best to play it safe by venting crankcase via a hose to underneath the bike (and close the petcock when parked).

Would recommend doublechecking to assure overflow tubes in float bowls are clear open and clean -- use wire if necessary, compressed air, and lots of carb cleaner spray (best to wear protective goggles when spraying with this toxic stuff). If the overflow is escaping via the overflow tubes through the bowl nipples, it should not be getting into the crankcase.

Post edited by: Patton, at: 2007/05/29 18:59

I was getting gas in my crankcase through the # 2 carb via the petcock. It wasn't shutting off and was leaking through the vacuum line right into the case. I though it was the needles or float level. My bike sat for years too. You can try a petcock repair kit, but that didn't work for me. If that's the case replace it or get a cheap valve to run inbetwenn in the meantime. A petcock is around $90.00 for the adapter and shutoff valve.

Skyman wrote:

bemoore wrote:

RonKZ650, thanks. I was hoping that was the case. I'm getting tired of pulling the carbs. But at least I AM getting faster at it.

Amen. The first time I did it, it took me almost an hour to get them back on. The other night, I came in from the garage and proudly announced to my wife that I just installed my carbs in about 5 minutes.

She was VERY impressed. :whistle:

You're much faster than me. I can get them off in 5 minutes. It takes about 15 to get them back on. My wife is impressed, too.:whistle:

Patton wrote:

Crankcase gaskets cannot keep fuel out.

That's good to know.

Patton wrote:

Would recommend doublechecking to assure overflow tubes in float bowls are clear open and clean -- use wire if necessary, compressed air, and lots of carb cleaner spray (best to wear protective goggles when spraying with this toxic stuff). If the overflow is escaping via the overflow tubes through the bowl nipples, it should not be getting into the crankcase. <br><br>Post edited by: Patton, at: 2007/05/29 18:59

I have verified by blowing through it that the overflow tube on the problematic carb#2 is clear.

Thanks for the info.

vach wrote:

I was getting gas in my crankcase through the # 2 carb via the petcock. It wasn't shutting off and was leaking through the vacuum line right into the case. I though it was the needles or float level. My bike sat for years too. You can try a petcock repair kit, but that didn't work for me. If that's the case replace it or get a cheap valve to run inbetwenn in the meantime. A petcock is around $90.00 for the adapter and shutoff valve.

I don't think the petcock has a problem. It doesn't leak with the fuel tank sitting on my bench.

bemoore wrote:

...I have verified by blowing through it that the overflow tube on the problematic carb#2 is clear....

Clear overflow tube on #2 indicates any excess fuel allowed into #2 float bowl is escaping through the overflow as designed and intended.

So this would cast suspicion on one or more of the other carbs for possibility of obstructed float bowl overflow tube. Would suggest the same good cleaning of overflow tubes on the other carbs also.

A carb may seem to perform okay with a clogged overflow tube and/or a leaking float needle/seat junction and/or a leaking petcock. But when parked, fuel from the open or leaking petcock flows through the leaking float needle seat into the float bowl. If the excess fuel can't escape via the overflow tube, it likely winds up in the crankcase.

Good Luck with the repairs!

Post edited by: Patton, at: 2007/05/30 14:03

Just curious, what is a crankcase gasket?

I am with george, seems to me if something is leaking in it would leak out also?