Carbs Flooding

[shenquay]

Bought my first bike this summer, a 1997 GS500. Bike died while riding this fall and I decided to work on the carbs. I did a lot of research on how to clean the carbs before I tore into them so I'm pretty confident in my work. When I opened the floats I realized just how bad the carbs needed to be cleaned. I decided to buy a rebuild kit off ebay as some of the jets were partially stripped and the gaskets were at best iffy. The kit I got had stock size jets. Putting everything back together went really smooth and I was thorough in my work wanting to do it right. However, once I got the carbs back on the bike the engine would rev up until i killed it. Long story short, both carbs are flooding. My last test I used the clear tube method on both carbs and fuel was rising about an inch above the gasket. I have the carbs apart again and I'm looking at the floats. I have them set at 14.9mm, which is what they were set to when I did the clear tube test. I tripled checked and everything is assembled correctly. If I blow really hard on the fuel line no air comes out but once I start lifting the floats air comes through, so the needles aren't leaking. Everything looks like it's set properly but my carbs are still flooding. Floats are in good condition, no cracking or anything. If the issue isn't the floats and the float needles what else could cause there to be excess fuel in the bowls?

Some more details:
The frame petcock had a leak and was leaking fuel down the side of the bike so I ordered a new OEM petcock.
The vaccuum hose on the left carb and the vent hose that goes above the airbox were both capped when I got the bike. I have tried uncapping them and hooking the vaccuum hose to the petcock like it should be but I still get flooding. I put the caps back on but made no difference.
Mixture screw is set to 3 turns out.

[herennow]

First, try knocking the carbs with the handle of a screwdriver - can get the float valve to seat sometimes. But I'm thinking that the float valve seat itself is possibly leaking. There is an o-ring under the float valve seat, Did you renew that also? IF it is damaged, fuel leaks past the seat even if the float is sealing properly. You access it by removing the seat retaining screw (JIS) and then gently tugging the seat up and out of the carb body.

this video may help

https://www.youtube.com/watch?v=nAe_5YwWoV0

Good luck!

[shenquay]

Thanks for the quick reply! I've seen that video which is what prompted me to blow on the fuel lines to see if any air leaks. Just from huffing and puffing I don't think there's a leak via the float valve. The rebuild kit I bought came with new float valves and gaskets.

[herennow]

Another thought, make sure the fuel supply and carb vent hoses have not been swapped.

[shenquay]

I double-checked and I had my lines right. I'm pretty sure I narrowed down the culprit today. I didn't have a chance to work on it over the weekend but I was eager to test some things. During my lunch break I did some tests. I took my carbs to the sink and ran water into the fuel line. I hooked up the clear tube to the bowl drain for a float height check. Sure enough, still an inch higher than the gasket. So it's not the line or petcock. Then I took the fuel line and blew into it and water shot out the other end of the clear tube. So the float needles aren't closing at all. I drained everything and opened the bowls and blew all the water out with an air compressor. I took the floats off and got a bowl of water. Holding the floats by the gaskets, I lowered the floats into the water. They both floated really well with a lot of buoyancy. Submerging completely, there were no bubbles coming from the floats. So the floats aren't leaking. I took the float needles and dropped them into the valves and blew into the fuel line. No matter how hard I tried I couldn't get any air flow to come through, so the float needles and float valves are good. Everything looks good which means the floats aren't pushing the needles into the valves hard enough to stop the fuel.

Looking at the metal tabs, both of mine bend in the middle of the tab.


Should they be straight and bend at the indents further up the tab?


When I get home I plan on messing with the tabs to see if I can get it to push down on the needles better.

[herennow]

Sorry, I don't know anything about those older carb floats and tangs. I'm sure someone will hop on and help you out.

Are BOTH carbs level one inch high?

Only thing I can think of is a damaged float needle end (the little black rubber part), or the little spring tube on the other end - does it move freely? Maybe you changed the float needle as well, if so, is the new needle the same length as the old?

[shenquay]

That's okay, I didn't know anything about carbs until I started working on this one. Thank you for your suggestions as I was kind of going crazy trying to figure it out by myself.

Both carbs are one inch high in all of my tests. I got two new float needles in the carb rebuild kit. From what I remember, the new needles were the exact same size as the old ones.

I did mess with the metal tangs on the floats yesterday. I straightened them out and then bent them at that indent I mentioned in my last post. I adjusted to about 14.8mm and tested but the carbs were still overflowing. So I bent the tangs really far down on the needles just to see if it'd stop fuel from getting into the bowls. Tested and no fuel was coming into the bowls at all. So at this point I think I just need to tinker with the shape of the tangs until I get something that works.

I should've done this in my first post but here's the kit I bought. When putting the carbs back together everything fit perfectly. The only thing the kit doesn't come with is new float bowl gaskets but mine are in good shape. The kit does come with float bowl o-rings but I used mine for under the diaphragm cover. When I first took the diaphragm covers off one of the o-rings was missing. The one o-ring that was there was the same size as the new float bowl o-rings so I thought that's what they were for. Didn't realize they were actually the float bowl o-rings until looking at the kit again on ebay.
https://www.ebay.com/itm/Carburetor-Rebuild-kits-for-Suzuki-GS500-GS500E-1989-thru-2000-2-Kits/382571815729?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

[herennow]

OK, I think I understand your problem.

I suspect that when you took the carb apart you found an o-ring IN the float valve seat. There should not be. There is an o-ring  AROUND THE OUTSIDE of the seat and you can see that in your photo. The O-ring that seals the diaphragm is tiny. there is no way it can be for the float seat (if that's what you mean by float bowl...I guess so)

"The one o-ring that was there was the same size as the new float bowl o-rings so I thought that's what they were for. Didn't realize they were actually the float bowl o-rings until looking at the kit again on ebay."

The viton rubber tip of the needle must seat against the BRASS of the valve seat, not against an oring.

If you do have an o-ring there that would explain why the tang bent and why fuel is leaking past.

[shenquay]

Not quite. I was talking about the o-ring I circled in this pic.



I double checked needles and valves and new ones are the same size as the old ones

[herennow]

Hi, can you explain then what you meant by:

The one o-ring that was there [under diapragm] was the same size as the new float bowl o-rings so I thought that's what they were for.

.

I think we are missing each other there. I cant see where such small o-rings would be used anywhere on the "float bowl"

[Kilted1]

Yeah, there shouldn't be an O-ring inside the seat of the needle valve.  There's one on the bottom of the seat to hold it into the carb body but the end of the needle is rubber so there's no additional seal needed there.  The little O-rings in that kit are for the vacuum ports on the diaphragm covers, and the pilot needle.  You have the O-rings on the pilot needles on top of the spring and washer?  (the washer there prevents the end of the spring from chewing up the O-ring)

Outside of that, you seem to be on the right path with your float adjustments.  It just takes some tinkering to get them right.     

[shenquay]

Sorry, that's my bad. Didn't proof read what I was saying. What I meant to say was I got new float o-rings (not float bowl) with the kit I bought. I didn't realize they were for the floats and used them under the diaphragm caps (the pic in my last post) since they looked like they were the same size.

Just for clarification, there is not an o-ring in the needle valve.

I messed with the tangs last night and think I got it adjusted good. I'm going to put the carbs on the bike tonight and give a a whirl.

[Kilted1]

Cool beans!  Be sure to let us know how it goes.   

[shenquay]

Well, as far as the issue of the carbs flooding it went good. Doing the clear tube test with the carbs on the bike and petcock on PRI, one carb is spot on and the other is about an 1/8 inch lower than the gasket.

When I started the bike with the choke on, the RPM's immediately jumped up to 4k and held. Before the carb rebuild it'd get to 3k with the choke on. So I'm not used to the RPM's getting so high. I turned the choke off and the bike remained at 4k. I let it run for about 15 seconds and watched the RPM's climb to 5k and killed it. Doing some reading later in the night I found that normal behavior is for the bike to idle at 4k-5k with the choke on until it warms up a bit. But since I turned off the choke it should've died and not stay at 4k rpm's (I'm thinking vacuum leak).

I did another clear tube test just to make sure and got the same readings, one carb spot on the other just a little lower than the gasket. I started troubleshooting the idling issue but I won't go into that since the thread is on the carbs flooding. I ended up pulling the carbs again and there was no fuel in the airbox like there was when it was flooding.

What I ended up doing was changing the shape of the tangs as the shape they were in wasn't pushing on the needles properly. I don't know how it wasn't flooding before because the new needles are the same size as the old ones. Below is the shape that worked for me.



The floats are currently set at 17mm, which seems high but hey, it's not flooding and the clear tube test looks good.