gas dripping from crankcase vent tube

[Guest]

I have a 1981 gs850. Ran fine. It sat for a few seasons in my garage..

I just rebuilt the carb completely, increased jets and added Pod filters.

It started right up and sounds good.. After a few min I noticed gas and smoke coming from the crankcase breather tube.. breather or vent tube used to goto airbox.

Any info would be great

Thanks
Costantino

[earlfor]

I have a 1981 gs850. Ran fine. It sat for a few seasons in my garage..

I just rebuilt the carb completely, increased jets and added Pod filters.

It started right up and sounds good.. After a few min I noticed gas and smoke coming from the crankcase breather tube.. breather or vent tube used to goto airbox.

Any info would be great

Thanks
Costantino

Welcome to the GSR!

Normally, gas must flow from the tank, through the petcock and into the float bowls. If the petcock is faulty, gas can flow into the crankcase through the vacuum line when the engine is not running. Also, if the carburetor float bowl needle "0" ring is not sealing, gas can also get into the crankcase. Those are the only two things I know that result in gas in the case. Additionally, if the float bowl needles are faulty, but the petcock is good/working properly, no gas will reach the crankcase oil because there is no flow from the tank when the engine is stopped. All gas is drawn/burned in the cylinders when the engine is running.
Short answer....change the oil and filter and replace the petcock. If the bike was sitting up for a period and there is gas in the crankcase, it is certain the petcock is the fault. That will stop the problem, even if the carb float needle valves do seep and need to be replaced.

It's preferred to post tech questions in the applicable technical forum, however, I think a quick answer is the easiest response. LOL

[Spyder]

I can't think of ANY scenario, where gas would come for the BREATHER tube from the valve cover... Unless the engine is FILLED with gasoline, and no oil at all? only 2 things come to mind. Are you sure that's where it is leaking gas, and... Are you REALLY sure that is where the gas is coming from?

[fastbysuzuki]

Got to agree with the other post if you have gas in the crankcase it's either from leaving the petcock on prime and the float valves have been passing, the petcock has failed either letting gas down the vacuum line or letting gas pass in the run position either way new petcock is in order + oil and filter change.
cannot see how gas is coming from breather other than already said the engine is compleatly flooded. 😳😳😳
is that an inline fuel filter in the picture if so it may not let enough fuel through to the carbs at higher revs.

[Costantino]

Thanks for the help

I changed the oil and it stopped!

Also, after I start it and switch the fuel value to 'on' it would stall out. I have to leave it on 'prime' to stay running..

I do have small fuel filter in the fuel line between the tank and carb.. is that causing my fuel valve prob? There is also filter on the fuel valve in the tank.

Thanks for the info.. much appreciated

Costantino

[cowboyup3371]

If you switched it to on and it failed then there is a problem with either the vacuum line between the carbs and petcock or the petcock has failed. And yes, get rid of the fuel filter - it's not needed and is likely adding to the problem

[Steve]

Also, after I start it and switch the fuel value to 'on' it would stall out. I have to leave it on 'prime' to stay running..

If you had to turn the fuel valve to "ON", you evidently do not have a stock fuel valve, as Suzuki did not offer one with "ON". The three positions on that model were PRIme, RUN, REServe. If it runs on PRIme, but not in the RUN position, there are a couple of possibilites. 1) there is a problem with the valve. 2) you are almost out of gas.

.

[fastbysuzuki]

Same has what Steve has said, have you got the petcock that steve describes? If not what do the marking say?
whatever you do, do not leave the petcock on prime when stopped/parked up or you could will fill your crankcase with fuel if the float valves are passing. Take it off prime to be safe on parking.
As for the fuel filter you could try it but if you have problems when running first thing to do is remove it.

[greg78gs750]

do you have the vacuum line hooked up to the carbs? is it kinked? hard to tell in the pic

[Costantino]

Thanks for the help.

I got rid of the extra filter and took apart the fuel valve. It was in bad shape so I quickly ordered a rebuild kit. That was easy..

So I get it started and when I give it throttle it boggs down, and no power. It happens almost at the beginning of the throttle.

I did adjust the pilot screws from 2 1/2 turns out, to 3 1/2 turns out. It seemed to idle smoother but no change when I give it throttle. When I rebuilt the carbs I did increase the main jets and pilot jets.

20190623_132421.jpg

[Costantino]

Also, since I rebuilt the fuel valve and it's working correctly, I just leave it on the 'on' position

20190621_172252.jpg

[Costantino]

Fuel valve .jpg

Fuel valve not original?

[greg78gs750]

i think we are gonna need more and more detailed info, re jet sizes, "rebuild" details, etc. Also, you "might" consider moving this to the carb thread, better chance of more pointed troubleshooting there....

[KEITH KRAUSE]

Smoke and gas coming from the crankcase breather tube means the crank was over-filled with oil and your petcock was leaking fuel into the crank. Both are fixed now.
With CV carbs, a torn/poorly installed diaphragm will allow a bike to idle all day but as soon as the throttle is touched, it stalls.

[Spyder]

You also haven't mentioned if you have raised the needles. This is a must with pod filters, and would likely cause the symptom you are having. Does this bike still have the stock exhaust? You should maybe run through the carb tutorial...