79 850G fuel leak. Please help

[AF_Bill]

I rebuilt the carbs on my 850 a month ago. I followed the steps from BassCliff's site as well as the repair manuel. Got them as close to OE specs as I could. Bike ran, but not 100%. So I took it to my mechanic who told me the valves needed to be adjusted before he could sync the carbs. Got it back last friday to find that I have a small fuel leak (again) coming from the #2 carb from the vent hose on the bottom of the carb. WTF.

[azr]

How is your petcock working? if you take the fuel line off the petcock does fuel continue to leak out (bad petcock can cause this. If it is the petcock check your oil to make sure there is no gas in it)? maybe the float on number two is set too high causing it to overflow out the tube? how did you set up the floats? manual measure or by using a clear hose from the drain plug?

[AF_Bill]

No fuel leaks from the petcock. When I was rebulidin the carbs, I didn't mess with the floats just cleaned and reinstalled them. They all seemed fine.

[Larry D]

Petcock......change your oil and filter after you replace it.

[AF_Bill]

Oil and filter was changed when the valves & carbs were synced and adjusted last week.

[Nessism]

No fuel leaks from the petcock. When I was rebulidin the carbs, I didn't mess with the floats just cleaned and reinstalled them. They all seemed fine.

How do you know the float height is "fine" if you never measured it?

And leaks from the petcock can not be properly tested until you judge if there is fuel backfeeding down the vacuum line and into the engine.

[Steve]

Oil and filter was changed when the valves & carbs were synced and adjusted last week.

That may be true, but if gas has leaked into the crankcase from an overfillled carb or leaky petcock, it's already toast.

Put the bike on the centerstand, check the oil level. If you have to tilt the bike to the left to get the level down to the window, there is too much in there, and there is a possibility that it's not all oil.

.

[AF_Bill]

Steve-So the carbs need to be rebuilt again? Whats already toast?

If I'm understandin ya'll correctly, replace the petcock, check the float levels, & change the oil?

[BassCliff]

Hi,

Assuming the carbs were rebuilt properly (and I don't doubt that) and all of the O-rings were properly replaced, I think these are your options as to causality:

1) Malfunctioning petcock.

2) Maladjusted float heights.

3) Improper seating of float valves (float needles and seats).

Click here for more information and solutions: Overflowing Carbs

It could be one, or a combination of all three.


Thank you for your indulgence,

BassCliff

[Lulu7404]

Sorry to highjack. I am having a severe leak in #3 carb while bike not running. I used a overflow tank from autozone as mentioned on a thread here as temp tank. Have fuel line running to one of the nipples on tank. Do i need to connect vacuum line to one of the other two nipples on temp tank or plug it? Seems to flow out of the vent T between #3 and #4 carb. Thx and sorry again, but hopefully these are same problem. New o-rings. If the needle seat got slightly out of round while taking it out with pliers to clean and replace oring, could that prevent the needle from stopping the gas from continuing to rise in bowl... sounds like I have to change the oil now.

[AF_Bill]

Ok. I'll start lookin into all these soon.

[BassCliff]

Sorry to highjack. I am having a severe leak in #3 carb while bike not running. I used a overflow tank from autozone as mentioned on a thread here as temp tank. Have fuel line running to one of the nipples on tank. Do i need to connect vacuum line to one of the other two nipples on temp tank or plug it? Seems to flow out of the vent T between #3 and #4 carb. Thx and sorry again, but hopefully these are same problem. New o-rings. If the needle seat got slightly out of round while taking it out with pliers to clean and replace oring, could that prevent the needle from stopping the gas from continuing to rise in bowl... sounds like I have to change the oil now.

Hi,

Yes, threadjacking can get confusing.

When I use a temporary tank, such as when synchronizing my carbs, I always plug the vacuum line to my #2 carb. Otherwise it throws off the measurements.

If your carbs are leaking then my previous post applies to you too. Yes, it is possible that worn float valve needles and seats will not close properly. Any foreign matter, rust from the tank or grunge from improperly cleaned carbs, can get stuck there a not let the float valves close. The parts from aftermarket carb kits can be ill-fitting and also cause leaks. It is highly recommended to use OEM float needles and seats.


Thank you for your indulgence,

BassCliff

[azr]

Getting lots of good advice here. To test the petcock just pull of the fuel line and set it to run, if no fuel come out that part of the petcock is working but Nessism is right you have to check that fuel is not also feeding down the vacuum line as well. Not exactly sure how to check that but I'm guessing if you start the bike and put on a bit of throttle so the bike doesn't stall, and just pull off the vacuum line and see if any fuel come out of that part of the petcock? What steve was referencing to as being toast was your oil. Once it gets gas in the oil it thins it out and you can really damage your pistons/engine. It could be a stuck open float needle, sometime a simple wack on the float bowl sets it again. Or it could be the float levels are off. Really the only way to properly set them is with the clear hose method. I do mine on the bench rather than back and forth to the bike.