Fuel in the airbox

[Lucien Harpress]

So, "simple" problem, hopefully simple solution, right? Let's see.

I found out today that, while in motion, my XS likes to leak gas out of the rear of the carbs. It's not so bad that it's dripping out the airbox (not yet, anyway), but I still get a bit of a leak from the airbox/carb boots.

When I stop riding, the leak eventually goes away. Am I correct in thinking this is just the petcocks doing their job, not allowing fuel through when not pulling a vacuum?

I'm just wondering what the heck is going on. This hasn't been doing this too long, and normally I would suspect float needles hanging up. Thing is, there's more than one carburetor doing this- although, I'm sure this could happen.

I have NO clue what the float levels are. I haven't changed them since I bought the bike, and there's been plenty of time when they've worked fine. I think I'm going to drain the carbs completely, just to get the float/needle moving, see if that does anything. In the meantime, does anyone else have some words of wisdom?

Thanks.

[prometheus578]

Yep, you're vacuum operated petcocks are doing fine. What's no longer working are you float needles. They're worn and not sealing.
Oh, they've been leaking for a while. Leaking while you're riding, but leaking just enough for your engine to still suck it in, but you've been running rich.
Now, they're to the point where the leakage fills the float bowl quicker than the engine can suck it out and the bowl is over-filling and you see leakage on the outside or fuel flowing out through the airbox.
Get some new needles, check the float height and all should be well again.
(Cheapest needles I've found were from "Z1 Enterprises")

[bikerphil]

Might want to check the O rings under the needle seats.

[Lucien Harpress]

I'd BETTER not have to buy new needles. I just did a few months ago, and they shouldn't go bad that quick!

I'll clean it out, but I really don't want to have to buy these things again...

[79XS11F]

I'd BETTER not have to buy new needles. I just did a few months ago, and they shouldn't go bad that quick!

I'll clean it out, but I really don't want to have to buy these things again...

If that's the case and this is a "new" issue you may want to confirm that the carbs are venting properly. If the vent hoses are blocked, kinked anywhere along their length the carbs will flood into the air box. Once you get this sorted out and confirmed as fixed you will want to check / change your oil.
Other issues can be fowled floats which can often be corrected by rapping on the carb bowls with the back side of a screw driver. Sometimes a needle will become fowled as well if the floats let them drop too far out of the valve. Rob

[ManagerMike]

Just a thought, floats dragging on the bowl gakets?

[CatatonicBug]

I'd BETTER not have to buy new needles. I just did a few months ago, and they shouldn't go bad that quick!

Did you replace the seats too?

[DenyP]

Have you installed in-line fuel filters? It don't take much crud to fowl up the needle and seat.

Deny

[fredintoon]

I'd BETTER not have to buy new needles. I just did a few months ago, and they shouldn't go bad that quick!

I'll clean it out, but I really don't want to have to buy these things again...

Hi Lucien,
didja change needles + seats + seat o-rings as a set?
What I reckon is, those parts wear into each other over time so replacing just the needle is a sub-optimum fix.
Did you trim the gasket's inside edge with a razor knife so it don't stick out past the carb bowl?
I have also found that running out of gas can let the floats down far enough that the needles can get misaligned and won't seal when gas gets added but that the old rap the carb trick works to fix that.

[Larrym]

Needle/Seat Seepage and Tiny Puddles.....

Did ya bench test for leaks before reinstalling the carbs?

http://www.xs11.com/forum/showpost.p...4&postcount=17

If not then....a bench test now to get your eyeballs on just exactly which carb(s) are doing what and where....

[81sx1100]

My 81 xs1100 was doing that even after i rebuilt the carbs and it turned out to be the petcocks were not working so i rebuilt the petcocks and there fine no gas leaks

[cywelchjr]

Doesn't matter if the petcocks are working or not, if the carbs are leaking when parked you have a problem with BOTH the petcocks and the needlevalve/seats in the carbs. You should be able to leave the petcocks on prime and not have any leaks. If you get leaks EVER, there is a carb problem, and you may also have a petcock problem. Properly working petcocks can mask a carb problem because they shut off the fuel when the engine is not running, but my petcock on my 400 (which same carbs with different jets and slide springs) was bad for YEARS and the carbs never dripped even once until there was a needle vavle seat problem (o-rings on the seats got compressed over the years) and when I fixed the needle valve seat problem the leaking stopped. THEN and ONLY then did I bother to work on fixing the petcock problem. Remember, carb leakage when sitting requires TWO failures, and you NEED to fix both, but IMHO the carbs are the #1 priority.

[Ken Talbot]

Remember, carb leakage when sitting requires TWO failures, and you NEED to fix both...

I'll second that!

[oldyam80sg]

And i would not want to ride if gas is leaking out even a little bit.Would not want anything to ignite.