I GOT IT! Maybe... Fuel issues, maaayyybe.

[Surly]

Okay, I was getting gas in the airbox on my 78 GS1000E so I put on a new petcock, pulled the float bowls (clean) and cleaned and inspected the needles. (Seemed okay, passed the blow test, less than a year old and bike was barely ridden.)

Put the tank on, hooked up the vacuum and fuel lines, turned petcock to prime and gas flowed into the carbs. Left it on prime for maybe 30 minutes. Turned it to on for 30 minutes. Turned it back to prime and left it for 15 minutes. Then, gas started dripping out of the tube on the bottom of the float on the far left carb (downhill on the sidestand).

Is this normal when left on prime? For the bowl to get over full and drain out that tube? Please tell me that is what they are there for! Unless it isn't...what...they...are...for. And then I still have problems.

Bike is waiting YOUR answers in the on position and a bucket under the hoses.

Thanks.

[chef1366]

When I prime my bowls I count to 60. More than that will but pressure on your float needle and seat that it can't handle.

[Dave8338]

There is also a relation between how much fuel is in the tank. A completely full tank is putting more pressure on the seats in prime, than a tank that is 1/3 full. Also, if you have a center stand, I'd use it. Seems to keep things more in check as compared to using the side stand. Just a thought.

[koolaid_kid]

Right, the cause is a slight leak in the needle and seat. Typical of your age of bike. Prime is just to fill the bowls, which does not take long at all.

[Surly]

So I'm okay then?

The tank has about 2 gallons in it, so that is about 1/3-1/2 a tank. I can totally see the prime setting overloading the bowls, and the farthest one downhill getting a little gas by the needle and burping out the vent tube.

So if I am reading you all correctly, I think I am good to go at last, as long as I keep it off prime except for those short bursts. When it was running last summer, I used prime once, and that was to start it for the first time since 1989. I know better, but I wanted to test the limits of the system out. I'm finally going to bolt it together, hopefully for the last time for a while, and ride and enjoy it.

Thanks for the support, you guys are like big electronic security blanket for a lot of people. I just needed some affirmation that it is good to go.

Thanks again.

[Nessism]

If your needles are working properly my understanding is that you should not get any leaking regardless of the petcock position or if you are on the side stand. I rode lots of bikes that did not have a vacuume petcock, on all the time, and I never had a leakage problem.

[nabrams]

Nessim is right. The vacuum petcock is a "safety" measure just in case your float needles aren't sealing properly, but ideally they should seal perfectly so that fuel flow is stopped. Having said that, it is true that many older bikes will not realistically have perfectly sealing float needles, which is why it's a good idea NOT to leave that petcock on "prime".
Also, if your float needles are leaking then it is likely (depending on the severity of the leak) that the fuel level in the bowl will be too high at times (like idle and low throttle settings), leading to rich running (and poor gas mileage).

[Surly]

I agree.

I agree with you guys that the carbs the should seal on prime. But right now they are sealing where it matters, on and reserve.

I simply can't justify the money to replace needles that are less than a year old and have two hours of ride time on them. I reset the floats at the high end of the measurement so I'll see what happens next.

It will be running down the road again today, and I'll see how much the mileage suffers. If it's bad, hey, what's another teardown? 8-[

Thanks.

[tkent02]

Your needles aren't bad unless they were defective to begin with. They can't wear out that quickly. It could have something stuck in it preventing a proper seal, or perhaps the little washer around the valve has a problem and is not sealing correctly.
There is another possibility, the fuel may be coming from an O ring on the fuel T.
If the O rings have dried out from the carbs sitting empty for a while, they can leak for a few hours and then swell up and hopefully seal correctly after that.
My '78 750 did that last fall when I came back from six months overseas.
After a little while there were no leaks at all.

[Surly]

It runs! then dies. then pukes gas all over when running.

Bolted it all together and took off down the road, it died about half a mile away.

Same problem as before new petcock. Wasn't getting gas to the carbs because the fuel line was too long, bad angle, whatever. Ran home, brought down the truck, had a new fuel line in place in a flash. Jumped on and it started right up. Rode around for about 15 minutes. Great. Solved. Ran great.

Took off again a couple of hours later. Got a couple of miles away and it started to act fuel starved again. Pulled over. Died. Got it to start on prime and rode for about a mile before switching to reserve as it only has about 1.5 gallons of gas in it. Again, very fast with gobs of torque,

Made it home and as I sat in the garage with the bike running I smelled gas. Sure enough, coming from the #3 hose on the bottom of the bowl. Shut it down and gas stops, fire it up and it starts flowing again.

Why didn't it do it on the earlier ride? All I can figure is contamination. So sometime soon (as soon as I am over my discouragement) I'll try and pull the bowls on #3 and #4 while on the bike. I'll switch needles and see if #4 becomes my problem child. I may have put #1 in #3 when I had them apart during the week.

ANY other idears? Here's what I've done (with the fuel system) so far:

- Dip and rebuild with complete kits from Dennis Kirk and
Mr. O-ring guy -5/06
- Radiator shop clean and seal tank -02/07
- New petcock 03/07

That about covers it. It is either a bad needle or some gunk in it. I lean towards gunk since the earlier ride had no ill consequences. Wish I could make a filter work. Even with the sealed tank you never know. Very discouraging. At least I have my Yamaha DT175 to ride now.

[bexabarr]

Are you setting the float height at the right level. I was having a similar problem and it turned out that one of my floats was way off.

[chef1366]

I think you have some crud in your float needles and seats or your floats aren't adjusted to spec.

[Surly]

Float height

The floats are set at at 7/8" - 15/16". I believe the service manual lists a range of .9"-.95" so they should be good. If those numbers are in in error, let me know.

Sometime this week I am planning on dropping the bowls while on the bike, swapping #3 and #4 float needles and, while they are out, turning the petcock to prime to maybe flush anything out.

Then put it back together. If #4 becomes the leaker then it will be time to contact z1 enterprises for a 6-pack of new float needles. If not, I hope something falls out of there so I'm no longer chasing a phantom.

[nabrams]

You did verify that the the float is floating, right? No fuel sloshing around inside the float (shake near your ear), right? Floats go bad all the time on these bikes (happened to me on several bikes). If so, get a used carb bank on eBay (probably cheaper than buying the float from the dealer) - one of the floats is bound to be good, and you'll have all those spare parts.

[Surly]

Thanks

I will definitely check the float for a leak.