setting float height?

[justmount1]

ok before i get to putting carbs back together how am i supposed to set the float height if there are only pins to hold them?

[Nessism]

[chef1366]

Notice on the pic that you measure on the stepdown of the hinge on the float body.

[Steve]

OK, to anwer your question along with the illustrations provided above:

Yes, they are attached by a pin. As you turn the carbs upside-down, notice that there is a small tab near the pivot pin that pushes on the float valve. The float valve has a center pin that is spring-loaded. Measure the height from the gasket flange of the body (without the gasket) up to the top of the float, not the top of the mount. The attached drawing might make it easier to see. To adjust the float height, bend the tab slightly to change the height of the float.

One thing that is hard for first-timers to grasp easily: this measurement is the distance the floats hang into the chamber. A higher measurement means the floats are lower, yielding a leaner mixture overall. A lower measurement is a higher float lever, yielding a richer mixture.


Float adjustment
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[Nessism]

Not to nitpick on Steve's very helpful post but... the mixture strength should not be affected by fuel height in the float bowl. Fuel in the bowl is drawn up via suction into the airstream so unless the fuel is overfilling to the point that it's spilling over into the airstream, or it's so low that there is nothing to suck up, it won't effect mixture strength.

[Reddawg]

Wow you guys are good. I was going to ask the float setting procedure on my thread 34mmcarbs.

[Steve]

Not to nitpick on Steve's very helpful post but... the mixture strength should not be affected by fuel height in the float bowl. Fuel in the bowl is drawn up via suction into the airstream so unless the fuel is overfilling to the point that it's spilling over into the airstream, or it's so low that there is nothing to suck up, it won't effect mixture strength.

OK, go ahead, nitpick away. 8-[

My thoughts on richening up the mixture might have more to do with timing than actual mixture. Since the fuel does not have to be drawn quite as high through the jets, it will come up easier and maybe a bit sooner in the throttle opening range. Overall, the amount of fuel drawn through will be limited by the jets, hence the mixture will remain the same.

I have no actual experience with this, but I did stay in a Holiday Inn Express last night, so I should know a lot about it. :shock:
I have seen several posts on this board hinting that the float level can/will affect the mixture, and that is my reasoning on why it happens.


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[justmount1]

so what should the measurement be on an 80 gs550L

[Steve]

so what should the measurement be on an 80 gs550L

Go to the carb sticky at the top of the Tech Info forum.
The first post just happens to have the specs for the '77-'79 carbs as the first item, followed by specs for the '80-and-up carbs.


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[bwringer]

Not to nitpick on Steve's very helpful post but... the mixture strength should not be affected by fuel height in the float bowl. Fuel in the bowl is drawn up via suction into the airstream so unless the fuel is overfilling to the point that it's spilling over into the airstream, or it's so low that there is nothing to suck up, it won't effect mixture strength.

Oh, yes indeedy, float height certainly and absolutely DOES affect mixture, at least on CV carbs.

Half a millimeter either way makes a difference in the low-to-mid rpm range. I ended up with mine set at 0.5mm below the lowest float height in the range recommended before I was happy with the carburetion. Lower float height (with the carbs upside-down) equals higher fuel level and a slightly richer mixture. Take the time, measure carefully, and get this exactly right. You'll be smoother, faster, and happier.

A couple of things I'd add:

1) Watch out for crappy aftermarket float needles. There's a little spring-loaded nubbin in the center of each float needle where the float tang contacts the needle. On GS carbs, this spring should be strong enough to hold the floats up when the carbs are upside-down without compressing at all.

I've encountered shoddy aftermarket needles that have weak springs, making it nearly impossible to set float height. Just imagine how long it took me to sort out exactly why the &^%$##!!!! my bike wasn't running quite right. Just imagine how far I threw the stupid things once I figured this out. And imagine how I felt when I realized that the only usable parts in $100 worth of rebuild kits were the float bowl gaskets ($4 each at CRC2).

There are some aftermarket needles that are OK, but it's hard to tell until you get them in your hands. (I got a set of high-quality new needles on eBay from a guy in New Zealand, supposedly from the OEM manufacturer.)

If yours have squishy springs, you could try propping the carbs up at an angle so the full weight of the floats isn't pushing down on the springs -- with some bikes this is the normal procedure anyway. I'm not sure how well this would work on a GS.

2) Make sure both halves of each float are set to the same height. This takes a little time and care to get right.

3) If you can find a small sensitive scale (measures 1/10 grams), weigh each float to make sure the foam hasn't deteriorated and soaked up gas. The floats should all weigh the same within a few tenths of a gram. You can also put a little gas in a jar and make sure each float floats at the same height and angle. I've encountered this problem on a car, but not a GS yet. It's worth checking, I think. I used an electronic postage scale.

[justmount1]

would it be a good idea just to buy new floats since the bike is so old and maybe the floats will go bad sometime soon?

[chef1366]

No. Very few floats go bad. It is just a possibility when trouble shooting.

[justmount1]

thank you i just wanted to make sure they weren't about to go bad

[justmount1]

ok i am a dumby what does this mean?
22.4+1.0(.88+/-.04)

[chef1366]

It's the variance of correct float adjustment. 22.4 is perfect but add .88 is ok and under .04 is ok. Same as spark plug gap. .024 to .028 will work.

By the way this number is with the float gasket off. Minus 1mm if the gasket is installed.