RE fitted carbs flooding. And I MEAN flooding.

Just replaced inlet rubbers, and cleaned out the carbs at the same time. Now after putting the carbs back in, which as you all know is just about the most fun the world can offer, the fuel just absolutely poured out - to the extent it was coming out the airbox drain. So I assumed I had a sticking float and took the carbs back out. To my horror , the floats all seem fine. No sticking no nothing. I WAS, however a bit bleary when I refitted the things, so what have I done wrong? The fuel was flowing from the auxilliary tank and onto the floor as though there were no floats in there at all. I know I am going to get a very simple answer to this problem and will kick myself when I get it. Thanks.

 

A float must have been stuck open. Did you tap on the carb rack with a rubber mallet or plastic end of a screwdriver. Sometimes one will get stuck when filling dry carb bowls.

 

what bike do you have will be the first question everyone asks.

either you've got bad float needles not seating properly. (sticking or dirt on the needles). or your floats are set WAY too high. or you've got brass floats that are leaking inside.

you could make sure your fuel switch is shutting off then you won't have that problem. but if your flooding out with the bike sitting. your flooding out with the bike running too. although it probably won't run.

if your floats are working and adjusted properly. your bike won't flood out even with the fuel switch constantly turned on. although not a good idea if your leaving your bike unattended for long winter months.

it's the job of the floats to let gas inside the carb. it's also the job of the floats to shut gas off when there's enough gas inside the carb.

 

Hmm.

Did you wet-check the float levels? Wouldn't it have puked all over itself during the wet-setting process as well?

 

Or the floats were installed upside down...........

http://mok.fileave.com/FUEL%20LEVEL%20draft%208c.pdf

 

upside down floats would be a BIG OOOOPPSSS.

 

Do you know something? I am a qualified mechanic. Though i did the course a few years ago. Let that be a lesson to you all. No, the floats are most certainly not sticking and neither are any of the gubbins that go with it. Unless of course I freed them without realising that. I reckon I must have set the fuel lines up wrongly, though I am sure I did not. This is a good site, and I appreciate the replies. Thanks to all of you.

 

i bet checal nailed it, my friend did that and i just bled fuel like crazy also check those little rubber things on top of the float needles, they tend to fall off and jam up the passage way

 

Every part of the float system needs a high level of fine sanding, buff, and polish.
*The inside of the "seat", both the surface that the rubber tip touches, and the sides, where the "needle" would slide. One trick is to use a sharpened golf tee in the hole. Twist it to polish the seat.
* the 4 little sides of the "needle" that would contact the brass inner bore of the "seat".
* The pivot pin, and the "bore" that it slides into, in the float. That would be the curled bit of iron. Iron rusts. Both the inside of the float bit, and the pivot pin need to be smooth
* even the rubber "Viton" tip of the "needle" can be touched up with 1500 grit paper, to give a new bite to an old part. This is done with the utmost care.

 

More importantly did the petrol find its way into the sump? :cry:

 

i know the feeling i had a set of 40mm hitachis off a virago. all of a sudden they started flooding over pulled them back off again major PITA you have to pull the intake rubbers off to get the carbs out will take a 4 cyl rack over them anytime i have done many carb rebuilds. put new needles and seats the whole 9 yards went to wet set them they were either to lo or they would get to a point then all of a sudden it was like you opened a valve up and over. even had a buddy of mine come over figured 4 eyes were better then 2 we spent an entire afternoon trying to get them set put another needle and seat in tried 3 different floats finally got to the point i gave up I had a set of mikunis from a later model parts bike cleaned them put them on had it over with. the only thing i could think of was an internal crack between the needle valve and main emulshin tube when it got up to about where it needed to be it hit the crack and went over that probably isnt your problem this bike sat in a barn for 10 years with gas in it it might have froze if it had water in the tank it was so plugged up it ruined the pet cock the fuel in the tank and carbs got rock hard

 

Oh, and I forgot to add, if these are Mikuni carbs, the float valves (the brass "seat") uses an o-ring to seal the sat to the carb bore, if those are bad or got torn during install, it will flood like a mofo.........

 

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I have had a lot of "qualified" mechanics make mistakes.

Even doctors make mistakes, with as much education they receive. Dont take it so personally if people point out the stupidly obvious solution to a complicated problem. Often, when working on cars or bikes, that is usually the solution that turns out to be the fix. But you already knew that ...right?

 

The rubber rings on the vavle seem to be the most likely source of the problem. I'll pull the tops off and have a peer about. They are Mikuni carbs, the bike is an '81 XJ550. The carbs with the unshiftable float pivot pins. Thanks for the sugestions. By the way , I was riding it regularly until the carbs came out, so the is no gumming up or anything.

 

And oh yeah, Id be astonished if fuel hadn't got into the sump, so its an iol change too. ( though i was planning on that anyway) Cheers.

 

One of the most common leaks ... after cleaning Mikuni's, ... is the Float Valve Seat O-rings.

If the Seats were "Easy" to reinstall, ... I'd go looking there and replace the O-rings with some New O-rings that cause a bit of a fight to get the Float Valve Seat back-in.

 

Thanks to all of you, and thanks Rick. I just took them to bits again, rebuilt, and filled the float bowls OFF the bike. No problems, no flooding, no leaks, nothing. Today , I'm putting them back onto the bike, and you can bey your house on it that they'll flood. By the way, I used so much carb cleaner on them that when I press the ignition The giantic blast ,fireball and sheet of flame will be visible round the world.