Gas dripping from Carbs

[ryonker]

I have had this recurring problem on my 78 that is really bugging me.

I have thoroughly cleaned the carbs and installed all new o-rings. Sometimes, after I have driven it or run the engine working on it, the carbs will drip some fuel. Not a steady drip. The fuel just seems to be seeping out from somewhere, and you can see a drip build up below the fuel screw.

I don't see any fuel leaking from around the T or gas lines. And my petcock is a pingle but I always shut it off.

When I rebuilt the carbs, I noticed that the float height was below spec. So I increased the float height to spec. I honestly can't remember if there was a dripping problem before I did this.

Could it be that the float height is just a little to high? It doesn't drip while running, only after the engine is turned off. It also seems like it is dripping from the fuel screw on the bottom of the carbs. Because of that, I replaced the o-rings on those a second time.

Any ideas for why/where the carbs might be leaking from?

Thanks!

Rick

[1978GS1000custom]

if you tap the bowl with the handle of a screwdriver does it stop leaking?

[ryonker]

if you tap the bowl with the handle of a screwdriver does it stop leaking?

I will try that. The problem is the leak is so slow and small. So you think the floats might be getting stuck?

[hampshirehog]

Could be your float valves are worn and letting petrol through. Or your floats are stuck (try tapping the bowls as suggested above). Plus your Pingel must be letting fuel through when you turn off (otherwise where would the fuel come from?)

[ryonker]

Could be your float valves are worn and letting petrol through. Or your floats are stuck (try tapping the bowls as suggested above). Plus your Pingel must be letting fuel through when you turn off (otherwise where would the fuel come from?)

I am pretty sure the gas flow stops when I shut off the pingel. But there is fuel about half way up the fuel line (I have that blue transparent fuel line). I can't see anything coming out of the pingel.

So, it is either, stuck floats or worn float valves. So my theory that it could be the float height is to high, is that not a possibility?

Thanks for the ideas!

Rick

[mike_of_bbg]

I doubt that your float height is too high; it would have to be really high to cause a leak like that. You know we hear about this all of the time with leaks from the airbox - which is usually a dual issue of bad petcock and leaking inlet valves. But even if your petcock isn't bad, there is still some fuel in the fuel lines after you (or lack of vacuum) shuts it off. You won't get enough fuel to leak through your airbox, but yeah on mine it comes over the sides of the fuel bowl (on the #1 carb only). I have a very pricey new OEM needle valve and seat on the way to try to take care of it. Usually takes 15-20 minutes after shutting off the bike, then I can go out and feel the side of the float bowl and feel it wet with fuel.

[Tom MLC]

Which carb is leaking? #1? when you set the bike on the kickstand, there is more static pressure in the #1 carb. Just like tilting a glass, the liquid is going to find a level, and it will try to be higher in the carbs on the left side. The needle and seat for the float bowl is metal-on-metal, as you know. Not a perfect shutoff. It would be very easy for fuel to seep past a worn needle and seat.

How 'bout when the bike is on the centerstand? Do you still have a leak?

[ryonker]

I doubt that your float height is too high; it would have to be really high to cause a leak like that. You know we hear about this all of the time with leaks from the airbox - which is usually a dual issue of bad petcock and leaking inlet valves. But even if your petcock isn't bad, there is still some fuel in the fuel lines after you (or lack of vacuum) shuts it off. You won't get enough fuel to leak through your airbox, but yeah on mine it comes over the sides of the fuel bowl (on the #1 carb only). I have a very pricey new OEM needle valve and seat on the way to try to take care of it. Usually takes 15-20 minutes after shutting off the bike, then I can go out and feel the side of the float bowl and feel it wet with fuel.

This is exactly it! It is most often Carb #1 and sometimes a little from Carb #2. It is does take about 15 to 20 minutes and then the bottom of the bowl is wet with fuel. It is never Carb #3 or #4. And yes, you are right, the petcock shuts off just fine but there is 5 inches of fuel in the line just waiting to drip down if it has a chance.

So likely this is just an old needle valve and seat deal. How much did they set you back...I may order some up. If I wasn't so anal, I would just leave it but I hate leaks and drips of all kinds.

Thanks so much!

Rick

[ryonker]

Which carb is leaking? #1? when you set the bike on the kickstand, there is more static pressure in the #1 carb. Just like tilting a glass, the liquid is going to find a level, and it will try to be higher in the carbs on the left side. The needle and seat for the float bowl is metal-on-metal, as you know. Not a perfect shutoff. It would be very easy for fuel to seep past a worn needle and seat.

How 'bout when the bike is on the centerstand? Do you still have a leak?

It really happens on side or center...but more noticeable on the side stand. I am betting it's a worn needle and seat for the float bowl. Yes, carb #1 is the worst offender.

Thanks Tom!

Rick

[mike_of_bbg]

So likely this is just an old needle valve and seat deal. How much did they set you back...I may order some up. If I wasn't so anal, I would just leave it but I hate leaks and drips of all kinds.

Yeah, I thought about letting it go. But it really hurts the mileage badly on my 5-mile jaunts to work to leak whatever is in the line each time! I have CV carbs, and the needle/seat set with an o-ring costs about $35-40 per carb (which is why I'm only going to do #1; we'll see if it moves afterwards). Pricey I know! Even the OEM o-ring is $5 or so. It's because they're genuine Mikuni parts. The o-rings for the cam chain tensioner were only about $1 each.

[Tom MLC]

Yeah, I thought about letting it go. But it really hurts the mileage badly on my 5-mile jaunts to work to leak whatever is in the line each time! I have CV carbs, and the needle/seat set with an o-ring costs about $35-40 per carb (which is why I'm only going to do #1; we'll see if it moves afterwards). Pricey I know! Even the OEM o-ring is $5 or so. It's because they're genuine Mikuni parts. The o-rings for the cam chain tensioner were only about $1 each.

??? Where are you finding a price like that? Try Z1 Enterprises. www.z1enterprises.com They have CV needle & seat assembly for $13 bucks each.