Two-faced symptoms

[Nightcrawler]

Mister Cinders

I just read this whole thread, I hope my 550 doesn't go through anything like yours is going through now I would lose my mind. But to note I had a hairline crack barley noticeable in the overflow tube on the inside of one of my bowls. It caused a fuel drip outside the bowl about where you are describing yours. At first I thought it was flooding until after a few hours i noticed the fuel level was normal when I took off the bowl yet it was still dripping. I just plugged it and am looking for a replacement bowl. Is it more of a sweat from the drain plug or actually pouring out?

[MisterCinders]

Just a slow drip that forms at drain plug. I've been watching the sides to see if gas is seeping out and forming at the bottom. The sides seem dry, so I think it's just that bowl. The plug and oring are fresh, so I am ruling them out as culprits.

[MisterCinders]

Getting warmer.

Put it back together and the bike starts and idles nicely. No more hanging, the RPMs move up and down with the throttle very crisply.

Synched the carbs and took a stab at the highest idle setting. Then noticed the No. 3 carb dripping fuel from the pod. Shut down immediately, and checked the oil smell. Thankfully, there was no gas odor in my new oil.

Pulled the rack and dove into the float situation on that carb. Inspected the, float, needle and seat and bowl again for obstructions. There is some crude or oxidation on one part of the bowl that has never come out (despite soaking, scrubbing, etc.). Just in case that is somehow snagging the float, I took another bowl from my set of spare carb parts, soaked it, scrubbed it and sprayed to get rid of the dust and grime it picked up while sitting around. I also swapped out the float with a spare.

The needle and seat pass the blow test, and I have a fresh washer in place. The new float is just a hair thinner than the other one, and moves nice and smoothly on the pin. The new bowl is nice and clean with nothing that could possibly snag the float (though I am not sure the rough surface in the other one really did anything).

Upped the float level from 23.5 to 24.5. Checked the fuel level with my drain tube, it settled in nicely at about 1-2mm down.

Put it back together again. Bike started and idled well again, but I still see some fuel spurts from the No. 3 drain tube. Nothing in the pods this time.

Tonight, I'll dive back into that No. 3 carb. Up the float level some more to about 25mm (top of spec), and triple-check the needle/seat and float level. Something's got to give.

Note that all of this happens with the tank off and to the side of the bike at roughly the operating height (maybe an inch or two higher), connected with a long fuel line, and the vacuum line plugged. So my petcock has no opportunity to fail AFAIK (fuel cannot be flooding through the vacuum line, since it's plugged).

I considered the choke assemblies, but have cleaned them vigorously and they all seem to move smoothly on the springs. Plus, IIRC a stuck choke would leak fuel into the venturi chamber, not the bowl. So a stuck choke might have caused fuel to seep into the pod, but not overflow the bowl itself. Is that accurate?

The float is the solid rubber version, so it cannot leak or take on gas through a pinhole, etc. Other than tinker with the height and hunt possible snags in the bowl, I got nothing. The old gaskets might have been catching the floats, but the new ones are a better fit. Each time I put it back together, I scrutinize the gasket edges to make sure the float clears. It has solid clearance on all sides.

If I am just chasing my tail on this, I am open to other ideas on reasons for this overflow problem. If the needle and seat continue to check out, and the float is moving without snags, what the hell else could be causing that carb to flood?

[MisterCinders]

I may have rooted out the last problem here.

Pulled the carbs again to figure out what caused No. 3 to overflow down the tube. Removed the bowl and set the rack up in a large plastic oil drain pan I've been using to test leaks and float levels for the carbs.

Ran fuel in the line and lifted the float to see if it leaked. Turns out the needle in that assembly was sticking closed AND the new o-ring I put on the seat was failing. So fuel would dribble into the bowl and never stop.

Changed that O-ring, reset the float to about 23.5 mm, checked the fuel level, and retested without the bowl. Now fuel flows through the needle valve (not around it) and stops when you lift the float.

Huzzah.

Didn't have time to put the bike back together and test the carbs on a running engine, but (fingers crossed) things are looking better.

Still cannot believe that when rebuilding/cleaning these carbs 3 different times in the past, all I ever needed to do with floats was measure and maybe slightly adjust them. Getting the float situation right on this go around has been an ordeal.

[BigD_83]

Why was the needle sticking?

"Turns out the needle in that assembly was sticking closed AND the new o-ring I put on the seat was failing."

Was there any indication as to WHY the needle was sticking? Was the o-ring so cockeyed that it was narrowing the seat space?

Good luck with startup. Sounds like you are almost there.

[MisterCinders]

"Turns out the needle in that assembly was sticking closed AND the new o-ring I put on the seat was failing."

Was there any indication as to WHY the needle was sticking? Was the o-ring so cockeyed that it was narrowing the seat space?

Good luck with startup. Sounds like you are almost there.

Not really. I have spare seats and needles, so I just swapped that set out for a set that moved more freely.

[Crankthat]

Saw a link to this post in a recent post i was reading. I was having a similar problem Carb leaking with my sisters honda after i had cleaned carbs. They were on 84? cm 450 with keikhin carbs. The carbs had a small (pipe) comming up from drain plug to normal fuel level so when they would overflow it would come out bowle drain plug-screw even when screw in closed position. The floats had no adjustment on them so i was looking at $72.00 a float after rechecking the float needles and seats a few times so i tried a few diffrent things first. Had a extra set of carbs for my 550 nighthawke all cleaned and wrapped in plastic the floats were diffrent but the seats and float needles were the same switched out still leaking went in for supper and not able to peel carbs off bike for another week so they sat with gas in them and not hooked up to tank. When i got back to the bike a week later it no longer leaked. My guess is that the rubber on the float needles had dried and mabye gotten harder then normal while not feeling so or atleast enough to stop needles from sealing correctly? Or might have had a bubble that had settled out during bike sitting have caused this? I dont know as i will ever know for sure but my float needles will forever after sit in gasoline while doing carb work... I know this is a old post but i thought it may help someone doing a search some day.