Leaking carb points of failure audit

[the schwartz]

Hooked up each carb separately to a clear plastic hose to check fuel level.

Three of them are the same height in the tube, right around the washer on the float bowl screws.

One does not stop taking gas and it overflows out the Venturi.

Will look at the following:

Float height set to 22.4mm +/-, with gasket removed (done)
Examine float, posts, for sticking (done)
Examine float needle for wear
Examine valve (the hole the needle does in) and spray (again) for debris, gunk that would prevent needle from seating properly
Check valve seat o-ring placement, regrease (have already replaced using cycleorings set)

Anything else?

*Edit: BS34 from 82 1100E

[Nessism]

If you have some gray scotchbrite it helps to take a small piece and stuff it into the float seat and then spin it around to polish the inside of the seat. At the end of the day though, if the float needle spring is weak and won't hold up the weight of the float you may wind up with a high fuel level.

[the schwartz]

Thanks Ed. I don't have any of that but can get some. I have 0000 steel wool but guessing that's a very bad idea

[Rich82GS750TZ]

I'm think the steel wool, being a harder metal that the aluminum carb body would probably do more harm than good, removing material rather than just polishing.

[the schwartz]

Edit. I figured it out and makes sense now.


I'm confused about your weak spring comment though... I thought that As the float rises, it compresses the spring until the needle seats fully in the needle valve, sealing the fuel passage. So a weak spring would cause the fuel to stop more easily, not overflow?

Did you write the wrong thing or is my understanding of these mechanics completely backwards...?

[the schwartz]

Yeah, I can't get it to stop overflowing.

Ordered some replacements off eBay, comes with set of four floats, needles and valves, a few other internals from someone parted carbs so hopefully something in that batch that will work as expected. Aiming to have this closed up by Tuesday wish me luck

[Gorminrider]

at the needle and seat? NEW seat+needle is best unless you are escaping the zombie apocalypse

My last resort when the zombies are banging at the door or I need my seagull o/b to stop poisoning the whales, is the finer valve grinding compound...and then finer than that to brasso etc. But it's iffy. If it's not a perfectly straight fit (needle-in-seat-as-you-grind) , it easily can make it worse.

[the schwartz]

Honestly the speed at which it's overflowing makes me think the floats are sticking and it's just open. It's a lot of follow.

We'll see it's my first time digging into this at this level though. Still learning

[Nessism]

Sometimes aftermarket floatbowl gaskets stick out too much and inhibit the float moving. Something to check anyway.

[bwringer]

BTW, aftermarket needles and seats are unmitigated, complete, 110%, utter, no-exceptions garbage.

Hopefully the ones you ordered are actual authentic Mikuni OEM.

One of the things to check is whether that little spring-loaded nubbin in the needle is able to move, fits closely so it can't get cocked sideways, and that the spring is strong enough to hold up the float with the carbs upside-down. And of course check for a good seal with the seat, and make sure the bore the seat is pressed into is smooth and the o-ring is correct and undamaged.

[the schwartz]

I did bugger up the o-ring on one float valve. How bad, think it'll still seal?0722192328.jpg

[the schwartz]

Is this kosher?
Check the angle on the float tang, I had to bend them far, onto the other side, to get my 22.4mm measurement. Same on each carb.

Just seems weird and like I'm doing something wrong... And most pictures I've seen, they're bent the other direction as well
0722192344.jpg

[Nessism]

Is this kosher?
Check the angle on the float tang, I had to bend them far, onto the other side, to get my 22.4mm measurement. Same on each carb.

Not kosher. Those are the wrong float seats/needles.

[bwringer]

Are you measuring float height at the step in the float?

And yeah, looking at your photo the float seat seems to be sticking up too far. Hard to tell for sure from here...




And yeah, that nick in the o-ring from a few posts earlier WILL leak. Profusely.

[the schwartz]

Yes, measuring it right at the step, per Ed's tutorial.

O ring: I'll have to email Mr Barr ask for another single

I got the other, used, OEM set of float needles and valves from eBay. The valves seem to be the same height but the needles are very visibly shorter in the OEM set than the ones that came with my bike. That would account for the ridiculous amount of bending I had to do on the float tangs to get to 22.4.

Here's a link to the stuff I got on eBay. Please don't make fun of me for probably wasting $50, I can do that myself anyway.

Question now, another question anyway, is what next. Buy a set of new OEM valves and needles would be best, also a bit expensive. The eBay set *might be fine but yeah...