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carb flooding problem - LONG

  • Thread starter Thread starter rkubik
  • Start date Start date
R

rkubik

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Well this one has me stumped, and any advice most appreciated.

Bike: 1982 GS650L

1. When I acquired this bike, it ran roughly. Took off the carbs and did a light cleaning with spray cleaner. When I put them back on, noticed fuel was dripping out of the airbox vent, so decided to do a dip cleaning as per the guide on this site.
2. Dip cleaned as per this site's guide, replaced all O-rings. When reassembled, fuel still pouring out as before.
3. Replaced needles and seats, using new aftermarket ones made in Japan. Also replaced the little metal gauze filters on each seat. Checked float level setting, set to specs in manual (21.4 to 23.4 mm). When tested on the bench with an auxiliary fuel tank, fuel still pours out the carb throat and air jet opening.
4. Tested floats to make sure they actually float. They do.
5. Adjusted float level setting to close needle sooner, no change. Adjusted many more times, still flooding.
6. Tested with float bowls off, holding needle valves closed by light finger pressure. Valves do close and shut fuel off, fuel flow resumes when floats allowed to drop.
7. Adjusted float level to much lower (i.e. valves close sooner) than manual specs, still flooding.

Still no joy. My only guess is that there is some "air lock" preventing the floats from rising enough to close the needle valve. But I don't know how to check that or resolve the problem. Anybody know what to suggest at this point? Thanks in advance!
 
what do you mean by float height being lower?

if measured the right way, which means upside down, that would mean the floats close with more fuel in the bowls....

but its late and im tired, i might have it backwards...
 
the petcock is not the problem, otherwise mine would flood as soon as I turned it to prime.

are ALL the carbs overflowing? id say even though the floats still "float" they may have lost bouyancy. that would explain why they work when you push em up with your finger and not installed. some chemicals you can put in your gas can soak into the float. some carb cleaners could attack em as well.

its such a simple system, as long as the hinge pins are straight and the floats are moving freely, and the valves are good, it should be able to have petcock "open" and not puke gas. think of all the bikes in the world that don't use vacuum petcocks at all.
 
Carb flooding. . ?

Carb flooding. . ?

I recently purchaced an 81 GS400L, and have just had the carb cleaned by a buddy of mine. . . . lots of crud came out.

anyway. . . I am now losing power at throttle around 5500 RPM in 4,5,6.
I am coincidently getting a "harley" like fwapping sound. I presume incomplete combustion (?)

Any ideas on treatments.

I did try running it up, and giving it some choke . . . but no real effect, nor change in sound.


Any advice appreciated.
 
yeah, but they usually have a "OFF" position, lol.

of all the bikes ive had, only yamaha and suzuki have had vaccum petcocks...

yeah icarus is right, if your float height is measured right (upside down) then its suff weighing down your floats... plastic is porous...
 
It's possible you may have shaved off a bit of o-ring on the float seats when you reinstalled them. It happened to me once. Coat the rings with a bit of oil to make them slide into their bores easier.
 
float height measurement

float height measurement

I'm taking float height measurement with the carbs upside down on the bench, from the base of the carb body (not the little ridge) to the flat metal piece on the float. Not the the bendable tang.

As far as I can make out, just as shown in the Clymer manual, and to those height specs.

Bought some little rubber vac line caps at the auto parts store. Will next try one carb at a time, with one side of the fuel line to the neigbouring carb capped off. And using low-odour varsol - those gas fumes are getting to me brain!
 
i thought you were supposed to measure float height upside down (as you're doing) from the carb body to the topmost part of the float (the bottom of the float really since we're upside down)...
i dont know what flat metal piece you're referring to but if it's the one connecting the floats together, you're off by about 10 mm on your float height and the floats will hit the carb bodies before closing the valve....
 
I will check this out ASAP!

I will check this out ASAP!

it has given me new hope.
 
keep us posted...

heres a page describing float adjustment in pretty good terms:

http://justkdx.dirtrider.net/floatlevel.html

i know its not for our bikes, but it gives a pretty good idea...

search the net, who knows, you might find your exact carb...

i dont believe in shop manuals, lol, nothing on my bikes ever seems to be stock.
 
Re: I will check this out ASAP!

Re: I will check this out ASAP!

rkubik said:
it has given me new hope.
Click to expand...
That's what I was thinking because others have made this mistake.
Without a picture, an error can be made trying to describe the correct measuring point. But as stated, you measure to the top most part of the float itself, not the bracket/arm that holds the float bodies. If you measure to the arm, you'll be very rich/high fuel level.
Hope that's what it is.
 
Rick, let me ask a question related to a personal stoopie I did on my own carbs recently after a rebuild. Do your carbs have a pair of tee's between each pair of carbs? In other words, is there a tee between the #1 & 2 carb, and another tee between the #3 & 4 carb? and if so, what have you got on those tees and where does it go? When I obtained my GS850 recently, those tees were simply open with nothing on them at all. I assumed they were vacuum ports and capped them. I subsequently had the exact same problems you did with fuel gushing from the throats. I went through several days of chasing my tail (which I won't inflict on ya'll here) but ended up uncapping the ports... oila! problem went away. They are intended to ventilate the carb float bowls. They SHOUL have a pair of long hoses on them, draped up over the airbox maybe and down towards the rear tire somewhere. They simply allow the float bowls to breathe (picture a drinking glass submerged in water, then slowly inverted and lifted out of the water except for the last inch of the rim... it holds the water completely till the rim is lifted from the surface of the water, breaking the vacuum). The ports do the same thing for the float bowls. A really simple cure in my case, which embarrasses me to share considering it took me 3 days to solve. But... no pain, no gain.
 
success

success

So I set the floats right, still no joy. All four still flooding.

Then pulled the hose joining the two bowl vent tees - as you say Dave, problem went away.

When I got the bike, there was a hose from one vent to the other. So I incorrectly assumed the hose should be replaced like that. Should have referred to the manual, now I know!

Once again we find "reassembly is not quite the reverse of disassembly."
 
wow!

glad you got it licked!

those hoses are meant to provide athmospheric pressure above the fuel level to "push" the gas through the jets... guess by making the system airtight you were pressurizing your bowls to the point where the floats couldnt rise.

bravo to dave for the insight!

incidentally, now that your flaot height is adjusted properly you might want to try a few plugchops to check if you're not runnign too lean (you must've been super rich before)

also, and this is VERY IMPORTANT:
if you flooded your engine because of overflowing carbs, you need to do an oil change right away, your crankcase is probably full of gas...
 
roger that!

roger that!

on the oil change, as it's about time to put it away for winter anyway.

Next spring, the plug chops! The bike actually has adjustable needles (5 clip slots) and low speed air screws so plenty of tuning is possible.
 
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