Stuck w/setting float height. 79'SF

[Gyrogearloose]

I've read Ken Talbot's tech tip on a rig for setting float height. My 79 doesn't have bleeder valve in bottom of float bowl. ? Am I stuck with tipping over carb and measuring the float height with a reference on gasket surface? This doesn't seem very accurate for 4 carbs.
On K. Talbot's rig, is fuel introduced to each carb individually? Like maybe a 90 where the "t" between 2 carbs usually goes? I'm probably having a "senior" moment here, and asking dumb questions, but........ Has anyone came up with a bleeder valve for early xs1100's?, and is the level in the clear tubing 3 cm below bowl mating surface?..I mean how full is "full" when the float and the needle do their jobs? (I think I just heard something go over my head). Heh.

[Ken Talbot]

Don't lose any sleep about not being able to check the fuel levels with clear hose like that post, Gyro. I played with that process only once and decided it was more trouble than it was worth.

I had way better luck setting the floats to the same height with a digital caliper, referencing to the carb body.

It really doesn't matter exactly what you set them to the first time as you're only trying to get all four the same. From there, you read your plugs, look at what you're got for jets, and see where your needles are set. In my case, I started by raising my needles a one notch to lean it out a bit. Still having black plugs, I raised each float by 2mm from whatever they were set at. This brought my mileage up by just about 10 mpg, and brought the plugs back to a perfect tan/light grey colour. That was the last time I messed about with the floats, jets, or needles. All I've done since then is sync it, colortune it, and keep the hairy foam filter element clean.

[81xsproject]

I went through all the trouble of trying this lately and was disappointed. I don't think there is very much inaccuracy involve in the height measuring process, especially if you use the end of a decent caliper to do it. The float needles used in the XS carbs have pretty stiff little springs in them and the weight of the float is not enough to even push them off their seat. I have tested this with my calipers in both positions of carbs resting on the throats and on their tops and the float height was exactly the same. As long as you adjust both sides of each float, the only other error possibilities are differences in the actual size/displaced fluid from one float to another or floats the didn't have the exact same mass as one another. Both of which would effect the buoyancy of each float.

So, save yourself a whole lot of trouble and just physically measure the float height. JMHO

Damn! Ken beat me to it

[Gyrogearloose]

Thanks Ken, your experience with this process makes it a lot easier for me.. and lining out the relevence with float height and needles, reading the plugs, etc. sure clears up a lot of questions that I may have had to ask. Appreciate it.

[Gyrogearloose]

Yup, Ken beat you to it, but your comments were a great confirmation, and you sure explained it clearly. thanks again to everyone who replys.

[SFerinTEXAS]

FUEL HEIGHT

Just for the sake of the first question in this post. Can anyone say how far below the carb body the fuel would most likely be as a rule of thumb? I'm a visual kind of guy and funny thing is I was pondering this same question minutes before I read this post. 79SF... I do recall the clymers on the 81 carbs says 2mm plus or minus 1. how about the 78-79 carbs? Anybody?

[thewiz]

that little spring ...

I've always been a little fuzzy on that little spring's function. As, 81 says, the weight of the float alone is not enough to compress the spring .... so what then is happening to the needle and seat/fuel flow while the little spring is actually being compressed by bouyancy of the float. Does the fuel shut off immediately as soon as there is pressure against the spring or at sometime subsequent to that?

[Ken Talbot]

Re: that little spring ...

Originally posted by thewiz
Does the fuel shut off immediately as soon as there is pressure against the spring or at sometime subsequent to that?

If it is not immediately, it must be pretty d@mn close to it. I would tend to so this against the springs, as this is what is going to be happening inside the float bowls when it is running - i.e., the floats are going to be rising up against the springs as they control the flow of fuel into the bowls. That's my story, and I'm sticking to it. If figure if I can get the floats within a few tenths of a milimetre of each other in the static condition with the weight of the floats against the springs, that's got to be pretty close. Anybody wants to promote the theory of testing with the carbs tilted so the float tang is just touching the spring without any compression, feel free to join in.

JAt, YMMV, etc, etc

[81xsproject]

Like I said, Ken. I've done it and as far am me and my 1/1000" caliper could tell there was no difference.

[boyat68]

In order to use Ken's method on my 80 G I use M8 grease fittings that I drilled out the steel center check ball and spring. The M8 threads fit exactly in the drain plug holes in the float bowl. On the nipples I use clear plastic tubing from Home Depot and Ty-Wraped a foot (12") piece on the nipple.

When I take off my tank, I place it on my WorkMate Bench so the petcocks are over the edge.I Ty-Wrap the carbs to a rod that I place under the WorkMate table top I connect the fuel feed tubes that I left on the carbs when I removed them to the petcocks. This way I can check the fuel flow through the petcocks as well as check the float level of all the carbs at the same time. When I am satisfied with the level on all of the floats, I remove the M8 modified grease fittings, leaving the plastic tubing on and store them for future use.

This beats trying to set the float level using the height (23mm) and then putting the carbs back on the Bike and testing them.

Thank you Ken Talbot!

Another trick is to take one of those simulated plastic credit cards or even a real one and using a measuring rule or caliper cut the card to the exact height measurement of your carb float setting, leaving a post on one side that square fits on the carb body with the top piece overhang that you can sweep over your float (a inverted L) height. This will allow you to try fit the settings on the first fluid check.

[Gyrogearloose]

Thanks for passing on the tricks boyat68; sounds good to me. Maybe I'll do'em when I get the IMscrew problem solved.

[TADracer]

I have never really done the tube from the bowl thing or anything else other than setting the floats from the gasket surface with a gauge. The clymers manual says (for a 79 SF) the float height should be 25.7mm +/- 1mm. I made several accurate gauges from thin sheetmetal in .5mm increments from 25mm to 27mm. I tried them all and finally settled on 25.5mm measured with the carbs upside down, floats resting on the little springs, from the gasket surface (gasket removed) to the top of the float. It takes a few minutes and a gentle hand but the results are very close and repeatable, if necessary. If I were just trying to get a starting point I would start with the stock setting as a baseline and work from there. And yes, 1mm will affect your rich/lean mixture so it is important that all floats are set as close as possible to the others.