Float heigh question

[Guest]

Am I measuring from where the float bowl bottom come off to the top of the floats. I say this becuase in my manual, it says measure withough the gasket. If measure with the gasket to take 1mm off the measurement.

Just a note, after reading the forum for this I know now that I should have measured and tested before cleaning. Too late, the carbs are now finally clean and put back together. I just want to try and make sure I attempt to measure the floats before I put the carbs back on.

thanks

[Steve]

OK before you put the carbs on the bike, you will have to turn them over and remove the float bowls. Here are a couple of illustrations to show what you need to do:

Measure to the top of the rounded part of the float, not the mount


I use a digital caliper by extending the slide and setting the tip on the carb body and measuring float height with the body of the caliper.


A closer shot of the measurement area: (if you look closely, you will notice that the gasket is in place)


Hope this helps.

(No, this rack of carbs is not ready to go on the bike. They were only used for the picture. 8-[ )

.

[maro]

EXACTLY what I wanted to know! Thanks. I also just bought an analog guauge. should work:-D

[waterman]

Just as Steve's great pictures and diagrams show where, how, and with what to measure, it is also important to know what you are measuring. You want to measure the float height as it is lightly resting on the needle valve. This is the hard part in measuring the float height--trying to keep float from depressing pin on needle valve while measuring. I find that by tilting carb body one way or the other I can get the float to just stay in contact with needle valve and carefully be able to measure height. I usually don't find that the heights are very far out of range unless some previous owner has really messed around with them.

What I do find important is that the floats are level in the bowls, they are often cockeyed (bent) and need aligned so they are float together. Secondly, if possible, set float height and then check actual fuel level in bowls. Try to get fuel level to be same across all carbs. This has a greater impact on tuning than relative float heights.

[Nessism]

Hope you pulled the pilot jets and pilot screws to make sure those circuits are clean. Also, the rubber carb "boots" have o-rings trapped between the boot and the head which are a very common air leak source. Changing them is almost mandatory on a GS if they are originals.

[maro]

Hope you pulled the pilot jets and pilot screws to make sure those circuits are clean. Also, the rubber carb "boots" have o-rings trapped between the boot and the head which are a very common air leak source. Changing them is almost mandatory on a GS if they are originals.

Yup. I cleaned everything on the carb. (dip) Changed all the o-rings. I just got my intake boots off today. I will now be replacing those o-rings as well.

I can't wait to get the carbs back on to tune.

[Smokinapankake]

Shouldn't be much "tuning" if no one has messed with them.

[bwringer]

I've found that 1/2mm adjustments to float height make an easily perceptible difference, so it's well worth taking the time to make sure they're all exactly the same. Just somewhere in the range given in the manual isn't good enough.

On my bike, I ended up with the float height measurement 1/2mm below the minimum measurement in the manual. This raises the fuel level when the carbs are right side up, and thus makes the low midrange rpm area a little richer and smoother.

Fiddling with float height falls into the category of fine-tuning -- everything else must be perfect before you fuss with this.

I also play with the idle mixture screws to smooth out the off-idle transition. Mine are somewhere between 2.5 and 3 turns out. (Stock airbox, jetting, and exhaust.)

The point of sweating these fine details is creamy-smooth transitions off idle and into the midrange. When you're leaned way over, you can get back into the gas much earlier, and fast cornering in general is much smoother and easier when you have precise and predictable throttle control.

And the spark plugs don't foul -- these adjustments only make things a tiny bit richer in the low end, not enough to change mileage or the color of the plugs.

The difference is easily perceptible and very useful, but it's a little hard to describe unless you've experienced it. It took three rounds of tweaking float height in 1/2mm increments to get my bike where I was happy with the low end, and each time it only took a 5 minute test ride to feel the difference.

When the road gets curvy, speed comes from control, not horsepower. Any goober can yank a throttle open.

[bwringer]

Hope you pulled the pilot jets and pilot screws to make sure those circuits are clean. Also, the rubber carb "boots" have o-rings trapped between the boot and the head which are a very common air leak source. Changing them is almost mandatory on a GS if they are originals.

That diagram is important for folks with BS (CV) carbs -- I worked on a set of GS850 carbs where someone had set the float height using the top of the float instead of the step. It ran a LOT better when I got done with it... :mrgreen:

VM carb floats don't have that step, so if your floats don't look like that, don't worry about it.