First attempt to start: fuel streaming from carbs

[Longitudinal]

Finally got everything together with the '78 GS750. Turned the petcock to "PRI" so the bowls could fill. A few seconds after I did this, I had fuel streaming freely from both of what I am supposed to believe are vent hoses and the bottom nipple on carb #2. A second attempt had fuel dripping from the #2 air filter (EMGO pods.)

The petcock seems to work, and it certainly works on prime.

Carbs are freshly rebuilt by somebody who has been doing this for ages.

What is going on here, and can I avoid re-removing the carbs and having them re-rebuilt?

[Agemax]

Finally got everything together with the '78 GS750. Turned the petcock to "PRI" so the bowls could fill. A few seconds after I did this, I had fuel streaming freely from both of what I am supposed to believe are vent hoses and the bottom nipple on carb #2. A second attempt had fuel dripping from the #2 air filter (EMGO pods.)

The petcock seems to work, and it certainly works on prime.

Carbs are freshly rebuilt by somebody who has been doing this for ages.

What is going on here, and can I avoid re-removing the carbs and having them re-rebuilt?

sounds like the float has stuck open on the carb, or is not correctly set. the carbs have to come off again to rectify the fault.
i would call your mate who has "been doing it for ages" and get him to sort it

[tkent02]

No rebuilding, just fix something inside that isn't working. Do it yourself so you know.
Try whacking the leaking floatbowl with the handle of a hammer or something, may knock the valve into action. If not, remove the carbs, drain them, remove the floats and their valves and see what's up. Something is stuck, or blocked open by a chunk of something, or very badly out of adjustment. Last time I found a small chunk of wood under the valve. It's something simple.

The first thing I would suspect is the guy that's been doing this for ages.

[supersonictoys]

make sure all bowl drain screws are tight, try taking a large screw driver handle and tapping on all of the bowls fairly hard in an attempt to jar the needles and seats to shut. if this doesnt work it sounds like the carbs will need to be pulled and the bowls removed and floats and needles and seats inspected

[Octain]

Hitting the carbs is highly not recomended.

Just my opionion though.

[Longitudinal]

Leak has slowed to a slow drip, but that could be because it has almost exhausted its fuel supply. Had a nice pool going on top of the transmission case. Still nothing but the occasional backfire, and the number four plug was completely dry and shiny--no fuel has been by it yet.

Drain screws are all tight now. One was slightly loose, but it was not on the leaking carb.

Inching closer and closer to a conversion to Bosch CIS. I sold my motorcycle just long enough ago that I had forgotten why and how much I hate carburetors.

[rustybronco]

GS750's will start and run just fine with the carbs on it.
and they're child's play to work on.

My friend Mr. Chuck working on his first set of carbs.
it started right up, the first time he hit the key.

http://s32.photobucket.com/albums/d44/rustybronco/?action=view&current=IMG_2001.jpg

[Nessism]

Hitting the carbs is highly not recomended.

Just my opionion though.

Sometimes the float sticks in the full down position after the carbs have been upside down on the workbench. Tapping the float bowl with a piece of wood or screw driver handle often frees up the float allowing it to drop down and start floating like it is supposed to. No worry.

[tkent02]

I sold my motorcycle just long enough ago that I had forgotten why and how much I hate carburetors.

Just go buy a new bike already.

[gearhead13]

Hitting the carbs is highly not recomended.

Just my opionion though.

Worked fine for me on my RM250 when the float stuck

[Longitudinal]

Just go buy a new bike already.

I'd sooner walk, which it appears I may be doing.

[Nessism]

Worked fine for me on my RM250 when the float stuck

Yup, standard procedure.

Regarding "hating carburetors", owning a 30 year old vehicle is not for everyone. It's best to either get something newer that will need less work, hit the lotto so you can shovel tons of money to your favorite mechanic, or learn to work on your own bike.

[bradleymaynar]

No one has mentioned this yet, turn the fuel tap to on. Unless I missed something.

Brad bk

[rustybronco]

I'd sooner walk, which it appears I may be doing.

No need to walk, you have everything you'll need to get it up and running...correctly; right here at your finger tips.

willing to try fixing it?

if so, read on...

did you rap the side(s) of the carb(s) as you were asked?

what has been done other than the pods? exhaust changed? was it re-jetted?

do you have basic hand tools?

[supersonictoys]

Hitting the carbs is highly not recomended.

Just my opionion though.

didn't say to beat on them with a hammer. just tap on them hard with a good sized plastic or wood item to jar the needle and seats and floats and this will hopefully get them to free up and seal. been doing it for 25+ years. I'm a certified motorcycle mechanic and specialize in 60's -90's vintage Japanese bikes. it works for me.