Float/Fuel Level issue

[81xsproject]

So I got some carbs from Andreas that I intended to clean and sell. But, they were in such great condition that I decided to keep them and sell my old ones. Here's the thing I am setting the floats and decided to use the leveling rack I made to do it the dynamic way with the clear tube up the side to see the ACTUAL fuel height. So, on my old ones I ran 23mm setting them statically with the float height. It ran great. I set one on the new carbs to 23mm as a starting point, closed'em up, put'em on the rack and measured the fuel height. The problem is that the one I preset at 23mm has the fuel level 6mm below the '3mm from the body' specified in the Clymers.

I just don't know what to do...

[DiverRay]

Are you running '80 or newer carbs?? If they are '78/'79, try running the floats so the fuel is higher. The carbs NEED to be set up per the year of the carb, not the year of the engine.
The internal design changes are the need for the float height difference, and should be taken into account. If you set all four the same, and it runs well, go with it. If you find you run out of HP at WOT, set the floats so you have a little more fuel in the bowel.
JMHO

[egsols]

You are measuring from the top surface of the float bowl?

Book also say to "run engine for 2-3 minutes" "to make sure float level is at normal operating level" Not exactly sure what they mean by this.....As the 81's have the vents incorporated into the body do they need a certain amount of pressure built up inside first?

Seems like a real chore, though, if you have to check them on the bike, levelling the bike etc., then pulling them off to adjust the floats, re-install, check again, repeat.

I like your idea of building a rig, just not sure about that point in the book about running the bike for 2-3 minutes.

[81xsproject]

I have the 80's carbs, I did indeed measure from the gasket mating surface. I am just going to try the 23mm and see how it goes. I was doing something similar to this old thread in the tech tips LINK

[Crazcnuk]

The entire reason for doing it visually, as your doing, is that you ignore the preset numbers and set them to the proper float height, regardless of what it might be.

Basically set the floats until you get the level, in the tube, where you want it.

[egsols]

Just got me thinking (not always a good thing)

What actually causes the float level to change over time? Is it just our fingers in there disrupting them during rebuilds? I can't see the needle wearing that much nor the clip stretching. If so then the only time we need to reset the levels would be after a rebuild or take apart for cleaning.

I'm thinking of putting 80 bowls on my 79 carbs so I can do the tube level check. If it works I'll be sure to take them apart after and measure the actual heights. That way next rebuild time I should be able to get them real close, hopefully.

[Crazcnuk]

As far as I know, the only time you have to set them is when you change the needles and seats, to compensate for differences in manufacture.

Brass floats either float or sink, so no changes there, but I have heard of some of the phenolic floats settling over time, perhaps becoming slightly saturated over time?

[red bandit]

I'm thinking of putting 80 bowls on my 79 carbs

81 bowls are the ones that have the tube hook up. 80-81 bowls won't fit on 78-79 carbs.

[egsols]

So I guess the only way of checking the fuel level on 79 carbs would be to replace the drain bolt with a bleed screw?

[81xsproject]

Clymer's specifies both measuring techniques for the '80 carbs in the supplementary section in the back with an emphasis placed on using the tube method. I don't see why they would be SO different.

As far as bowls go, the set of 80's carbs I went through recently that had brass floats also had the bolt drain bowls. In using 80's gaskets on 70's carbs, the only difference I could find was that the brass tube that goes down into the passage containing the stater jet is just slightly more towards the center of the carb body. What all this means, I don't know. But if Red Bandit or others have tried the bowl swap, they would know better than I.

[egsols]

Maybe my spare set are 81's. I thought the 80 carbs went to the plastic floats and drain screw The bowls looked the same as my 79's but I haven't actually checked whether they would fit , I just assumed.

[John]

I have tried to fit some 81 bowls on 79 carbs also...no way. The choke pick up tube and associated port in the bowl have been moved ever so slightly, and there is no way they will interchange.
The plastic floats were first used on the 80 carbs. A PO may have swapped them over at some time. I have 78 carbs on my bike with the plastic floats from a set of 80 carbs. I set them to the spec of the carbs they came from because of the differnt type of mount used to secure the plastic to the metal.

[egsols]

Thanks John,

That'll save me a bunch of grief.

In your opinion what do you think of using bleeder screws, in place of the drain bolts on the 79 bowls, to actually check the fuel level as opposed measuring the float height?

[John]

Do you plan on leaving them in place all the time, because I don't think brake bleeder screws will work, because they need a tapered seat to stop the flow. The 80 bowls have a drain plug, and the 81's have the nipple to attach a hose to and set the float height using a piece of hose as a manometer.

[egsols]

Once again I haven't thought everything through. My mind is as cluttered as my garage at times. I seem to recall seeing a type of bleed screw somehwere that was like a bolt inside a bolt. I' dont know where or what it was for but something it the back of mind came forward when I was looking at the current bolts in the bowl.

If I figure something out it will definitely make back here!