Mindbending Fuel Burping!

[PAGS550]

Long story short; bike has been sitting since 81, it's a 77 gs550. Used sea foam, got engine started but would not run well at low RPMs, also I believe fuel was coming out of the overflows underneith the bowls. Took carbs apart, cleaned everything in the bowl, took ALL jets out, used solvent, blew out with air hose, and reassembled. Bike runs excellent, doesn't seem to rev high enough when starting with choke though. hard to start. After riding for a few minutes, parked the bike and the fuel flows from the overflow hoses sporadically. It seems that every 20 seconds or so a big gush of fuel comes out..

I tried taking the gas cap off, no change, tried removing the vacuum line from the petcock, no change.

I took the carbs back off, set the float heights with my mic to .95". they were all a little high to start with for some reason so i thought i had fixed it.

Keep in mind, this bike has 1834 original miles, and shows no signs of having been torn apart before.

Put everything back together, and sure enough, hard to start, very low idle when on choke, and still spurts gas every 20 seconds or so, seemingly until the tank is empty.!!!!

What is going on! Thanks in advance for any help.

[SqDancerLynn1]

did you clean the float valves in the carb ? Check the airbox for air leaks, Check the petcock operation.

[PAGS550]

All four carbs have had the float needles and seats cleaned thoroughly, the petcock was a suspect but with the vacuum line disconnected i don't see how it could be the problem even if it was faulty... what would i look for in the airbox? I have similar carbs to this in my kz900 and i don't even have an airbox.

[PAGS550]

how do i know if the petcock is faulty?

[PAGS550]

well the vacuum line that leads to the carburetors from the petcock is clear, blew through it... this is amazing....

[TheCafeKid]

The petcock is bad if it flows gas without the motor turning over in any position other than "PRIme"
Besides cleaning the float seats, the floats need to be measured and set to a specific level to assure proper shut off by the float needle. Like the tank on your toilet.

[PAGS550]

Well the floats have all been set at exactly .95" so it must be the petcock? It DOES flow in all positions... I don't understand how the fuel can be getting past the floats though... aren't they supposed to stop the fuel when it gets to the proper level, just like a toilet ?

[PAGS550]

I'm used to the ones that are "on" "off" "res"... and even if you leave them on there usually isn't a massive hemorrhage of gas under the bike... I guess it was even leaking while riding a little bit. so it leaked right out of storage for sure, leaked after the first rebuild for sure, and leaked after making all of the floats exactly .95... could it have something to do with the choke circuit or the screw on the bottom (not in the bowl but in front of)? maybe the screw on the side?

[TheCafeKid]

I'm used to the ones that are "on" "off" "res"... and even if you leave them on there usually isn't a massive hemorrhage of gas under the bike... I guess it was even leaking while riding a little bit. so it leaked right out of storage for sure, leaked after the first rebuild for sure, and leaked after making all of the floats exactly .95... could it have something to do with the choke circuit or the screw on the bottom (not in the bowl but in front of)? maybe the screw on the side?

Just pop the fuel line off and see if the petcock runs in either RES or ON without the motor spinning. If it does it's trash. The float needles will hold back fuel for a while but they're not meant to do it forever.
And the floats should be set to 22.4mm ( +/- 1mm) from the float bowl gasket seat (not the gasket itself, take that out) measured from behind the step on the float itself (each side) turn the body upside down and measure with the depth gauge on a set of calipers. Very important they're set correctly, or it will leak, and of run richer or leaner.

[PAGS550]

Thank you "thecafekid" and "SqDancerLynn1"! I will rebuild the petcock... I know its bad because it does flow fuel all of the time. Do I need a whole petcock? My dad put a new gasket set on before we started the bike because it was leaking terribly already, and that obviously didn't help the constant flowing issue.

[keman]

While you have the carbs off the bike, try going through them completely. There's a great tutorial on the page that's linked in my signature. Doing it part way or taking shortcuts with the carbs on these bikes is always the road to doing it again later.

There was a guy on here a while ago, insisted he had cleaned his carbs, but kept having Carb issues. .. turns out he had run them with seafoam, and sprayed Carb cleaner into the intake. weeks of frustration later, he read the tutorial, did them the right way, and now has a well running bike.

Don't forget to replace the intake orings.

[keman]

Revving with the choke on is not going to give you any real info feedback.

Bad petcock can cause gas to leak down into your oil, over filling your case, damaging seals, etc... Most of the rebuild kiss are no good. I ended up buying a whole new unit from Suzuki, a bit spent, but worth the peace of mind.