Carburator Overloaded

[CaliforniaRider]

I have a '80 Special and can't figure out how to keep it running. It starts fine and runs well for 10 to 30 seconds then overloads with gas and quits. I have replaced the needles, checked the floats and reset the float height, to no avail.
I did get the carburators gone through and he found a leaking diaphragm. But it still won't run. Any ideas?

[mro]

I did get the carburators gone through

Could be da problem

Carb float height about 23mm. (see tech tips at left)
Check both sides each float?
Fuel mix screws about 1 1/4 out?? (fine tune later)
Pre-sync carbs??? bread tie works, (vac sync after running)

Hi ya CaliforniaRider

where abouts in Nor Cal




mro

[prometheus578]

" Ah, there's nothing like having to do them yourself."

runs well for 10 to 30 seconds then overloads with gas and quits

Sounds like the carbs are flooding. MRO's tips are correct. You need to pull the carbs and recheck everything. What you didn't mention... is fuel leaking out of the carbs when this happens?
You mentioned you replaced the needles, and such, which is the correct thing to do, but did you bench test the carbs before putting them back on?
Recheck the float height, and with the bowls still off and the carbs upside down, hook up a fuel source and watch them for a while to see if the float needles are sealing. Put the bowls back on, turn the carbs right side up, and watch if fuel comes out the airjets on the airbox side o' the carbs.
The bowls need to be vented, too. On the early carbs there are two tubes that provided a vent to atmoshpere... they are above the lower tubes that supply the fuel.
What makes you think they are overloading with fuel? Is it fouling the plugs? Or is it running well, then when you turn off the choke it dies, and you're just thinking that it's overloading? That's a different problem. Then it would be fuel starvation in the choke circuit, usually caused by a plugged jet in the float bowl(That little hole at the bottom of the bowl)

[acof911]

Could be the o-rings on the needle seats-see the photos in this thread

[prometheus578]

That's true, too, Acof911. T'is why one always checks the carbs for leaks before putting them back on the bike. (Unless one likes to practice taking them off and on several times)

[81xsproject]

Hey Nor Cal where you at? Have you put your self on the frappr page yet?

[Ken Talbot]

Re: Carburator Overloaded

Originally posted by CaliforniaRider
then overloads with gas and quits.

So what does it actually do? 'Overloads' really doesn't tell us too much. Does it rev up real high then just quit? Does it make a sputtering noise and slowly fade away?

[TopCatGr58]

Hey Prom,

He's got an 80SG. IIRC, they had the newer styled floats, plastic type, not solid brass. Another thing to check is whether the floats actually float! I think it's more rare for these newer styles to develop a leak but anything is possible!

CaRider, when you take them back apart, shake the floats next to your ear to "see" if you can hear anything sloshing around inside them!? Also, make sure the floats pivot easily on the pins, not getting bound/ binding against the float bowl.
T.C.

[CaliforniaRider]

Reply from California Rider

Thanks for the ideas. I had set the float at 26.5mm (from 25.7mm) trying to lower the fuel level. Am I going backwards? I will try the 23mm, but couldn't find the tech tip about float height.

I will check the needle and seats for leaks before reassembly and set the float at 23mm. The floats do float (plastic type) and don't seem to have any gas in them.

Is all this pre-sync, sync stuff necessary if the bike ran well before? Sounds too complicated.

By the way, I live in Santa Rosa. I would like to get the bike running and feel confident in it to ride to Tahoe with some of you around Labor Day. I went there before and had a great ride; there, back and around (including State LIne).

[Ken Talbot]

The pre-sync may not be necessary if you have the mercury sync tool do use immediately. What it does do is get your carbs somewhat close to sync although it will be idling very high.

The funny thing is you could run one of these machines on only two cylinders and still think it was running okay if you did not know any better. More than one owner has done this, only to have their eyes opened wide when the other two finally came to life! Sync'ing the carbs is much like that too. If you you've never ridden one with the carbs properly sync'd, with the floats set just right, with the correct jets, and with the pilot screws right on, you wouldn't know what was missing. It sounds more complicated than it actually is, and if you run into trouble, you can come here for help.