The International CBX Owners Association

All six of my stock needle & seat assemblies were gummed up, so I got a set of the replacement assemblies from TIMS. Tried setting my float levels at 15.5 mm (stock), 18mm (fairly low) and even 20mm (REALLY low) but the gas pours out the float bowl overflow tubes. Is there an optimal float level setting for these needle-seat assemblies? Danged Honda ones are $48 EACH and I'd like to not pony up $300 if i don't have to.....
BTW, I even went so far as to block the carbs up, hook up my aux fuel tank, hold the floats up all the way, and turn on the fuel. They do in fact stop the fuel flow when they're all the way up, but maybe the geometry is different enough to invalidate the factory float level setting????

Are you sure your vent pipes aren't cracked? Seems to be pretty common.....

Actually, yes, took one of the float bowls and filled it with gas (originally to make sure the drain screws were closing completely and the fuel stayed in the bowl just fine. This seems to be a float level error, and I'm kind of wondering if the aftermarket needle & seat assemblies change the geometry of the float any?
Latest guess was to keep lowering them til they don't leak....

big al wrote:I'm kind of wondering if the aftermarket needle & seat assemblies change the geometry of the float any?

Yes they can be different as I recently bought some aftermarket float needles ( not the ones from TIMS.) I am using stock Keihin needles in Mikuni VM29's. Why you may ask ? The are neoprene tipped & shut off better than the FMJ Mikuni needles. Length &/or spring tension may be different, which is what I found... Length is crucial as the angle of the float bendable tang has to be a perfect ( shallow) angle for positive closure..

The one thing I DIDN'T pay much attention to was how much force it took while holding the floats shut to make sure no fuel was getting thru. That'll be my NEXT test.....

Thanks much! Onward & upward.

Don't forget that they need to shut off against a full tank of fuel head. You will find the shutoff will improve over time as the soft tips form to the seat.
Look at the angle of the bendable tang, side thrust is working against you, they need to hold a shallow angle over the sprung needle plunger...

Yep, and this isn't a little seepage...it's flowing out of all six bowl drain tubes as fast as it goes in. (Fuel delivery is clearly NOT a problem on this one!!) Big question....if the angle of the brass tab isn't optimal, what can you do about it? Not a whole lot of options beyond bending the little tab.

So my next plan of attack, since the carbs are still in 'bench-test mode"
is to keep lowering the float levels til it doesn't overflow.
Any suggestions??????

Do you still have your original needles? Clean them with Berryman's B-12. Soak them for a day. Make sure the spring loaded button on the end moves freely. Put them back and you will probably solve your problems. I resurrected several needles which had been in a set of carburetors which had sat out in the weather, had water in some of the bowls, and were just filthy. All six of them are now working fine and have never leaked a drop.

Thanks for the reply, Spencer! I did in fact perform a test where we hooked up fuel to the carbs without the float bowls...held all six floats in the "UP" position, and the needles do in fact stop fuel flow with the floats up (this took about 3 sets of hands!!!) So they don't even seep a little when you hold them up. I'm kinda wondering exactly how low a float level I can get away with at this point, since the factory 15.5mm recommendation is clearly not working anymore. Other thing I didn't pay much attention to is how much pressure I had to put on the floats, but the carbs are still on the bench so I can try it again. I am kinda pointing the "big finger" at spring tension right now.

I'm following along.

Please don't stop, your comments are invaluable to someone that's getting ready to resurrect a couple 81 CBX's.

This is great.

Floats ? I'm not sure if they are foam filled but there is a possibilty that they have leaked ? Leave to dry over night & dunk in hot water & look for a gasoline bloom on the water surface, not sure if you would see bubbles as in leaky brass floats but just maybe ??.

To the best of my knowledge they are hollow (no foam). What's odd is, maybe I can understand one or two of em leaking, but all six? Highly unlikely. Other thing is, I was having this issue with the stock (read: gummed up!) needles & seats, and that's why the aftermarket ones, they cost 20% of what the Honda ones cost!!! BUT. After all the fiddling around I'm still right where I was 2 weeks ago.
Playing phone tag with Preston at TIMS, will advise when we finally hook up.

Just covering all bases..

The needles also have seat/guide bodies mounted in the carbs. Not too familiar with Keihins but on Mikuni's there are gaskets involved in the "assembly" .... also the seat width is critical. Too wide & it will leak, too narrow & it will prematurely wear the soft needle tip.

Of course, if the seat is cut/grooved or scoured it will leak. Seats wear over a long period of time as they are soft brass. This is due to long term mechanical contact with the needle & minute abrasives/solid particles in the fuel.

Are the "seats" leaking, worn gaskets ( if they exist) passing ??

Clear plastic tubes on the float bowl drains will enable you to clearly see the errant float chambers easily, without tedious disassembly..

No matter, Preston will sort it...

...

Brand new needles AND seats (from TIMS), and I went thru the carbs VERY carefully to ensure everything is in place.
Here's what Preston thinks....when you first put the float bowls on & flip the carbs right-side up, the floats drop ALL THE WAY DOWN, so he thinks maybe the needles aren't going perfectly straight into the seats...tap on each float bowl & shake the needles loose so they WILL close and we should be fine.
Makes perfect sense, in fact, the #1 float in particular seems to bind a little bit when you go from right-side-up to inverted, where the other 5 tend to fall pretty consistently. Also, the carbs are still on the work bench WITHOUT the 6-1 junction, so you can observe which one is the culprit (all of 'em in this case...)
Incidentally, compared the new aftermarket assemblies with the original Honda needle & seats, and all my measurements say they're identical.
The bike's at the bike shop, so I can't test this theory til Tuesday, but I'll be sure to keep you posted.
Thanks for all the input!!!