More Carb help

[motoman]

Point of order here...

Shouldn't the float height be set with the carb bank at an angle so the tang just touches the needle spring, but does not compress the needle spring?

At least that is how I have done it based on instruction from folks that know more about this stuff than I do.

When the carbs are turned completely upside down to measure float height, that is a lot of weight from the float, relatively speaking, compressing the tang into the needle spring nub.

Ok, let the beatings begin...

Good point Howard!..........and is how every PROFESSIONAL bike mechanic says its to be done also. I'll be goin' back to that just to be sure of initial setting. I think Clymers and other off the wall manuals indicate the upside-down thing, so that's become urban gospel......least here, thanks to the other mis-informed BS in those manuals(swing-arm torque specs, among others), which unfortunately I have assumed correct associated with the float settings. Again, when I get back from trip, I'll be doing that AGAIN, according to how I always previously understood them to be done......not from some second-rate manual. We'll then see where that actual 'running fuel level' ends up........also beginnin' to think that 23mm setting for the later carbs from THOSE manuals was pulled out of who knows where, and may be associated with so many here havin' to twist out those mixture screws on the later carbs WAY beyond the 2.5turns max. indicated for ANY bike sidedraft/downdraft carb........who knows, but I'm fixin to resolve this seeminly ongoing issue with the later carbs, includes others besides mine.......a little slow getting 'on task'....but once there, no mercy. "I'llllll B bok".

[skids]

Point of order here...

Shouldn't the float height be set with the carb bank at an angle so the tang just touches the needle spring, but does not compress the needle spring?

At least that is how I have done it based on instruction from folks that know more about this stuff than I do.

When the carbs are turned completely upside down to measure float height, that is a lot of weight from the float, relatively speaking, compressing the tang into the needle spring nub.

Ok, let the beatings begin...

I have heard that and done that. The tough thing about it is actually measuring the float height when everything is at an angle.

[3Phase]

Point of order here...

Shouldn't the float height be set with the carb bank at an angle so the tang just touches the needle spring, but does not compress the needle spring?
...

Bonz,

It doesn't matter. I've done both. It doesn't matter.

If the suspension won't correctly support the motorcycle would you try to lift it up and hold it at an angle with the tread just touching the pavement to set the ride height? It's not exactly the same for the floats and the needle springs but it's close enough.

Normally, the plastic floats won't compress the float needle springs and neither will the brass floats unless they leak and fill up with fuel or if they've been repaired and they're 'heavy' with solder. If a float needle spring is sticky or too weak to support the floats, try soaking it in carburetor cleaner or EvapoRust. If that doesn't work, replace the needle and don't try to tune around it.

Personally, I gave up trying to set the all of the float heights to less than a gnats wing. Set the float heights to somewhere within the allowed range and make sure they're not bent or twisted. Put the carburetors on the engine, level the bike and check the running fuel level in the float bowls. You can leave the airbox off while you're first setting the levels so you don't have to fight with it.

Put the airbox back on, synch the carbs and set the mixture screws, then go for a ride and check the spark plugs.

.

[Bonz]

It's not difficult to prop the carbs up, or simply hold/balance them at the angle where tang touches spring nub and use the other hand to position the float gauge for a reading.

Personally, I find the angle where it just touches, and manually compress the spring with pressure on the float a few times to get a good look at the point the spring is gonna start to compress. It's easy to "walk it in" and get the float height reading on each carb.

Once the heights are set, you can eyeball them all together and verify they are touching the same amount at the same time. Also sight over the floats, and they should look very uniform in height and alignment.

Edit: 3Phase, I have seen the weight of the float compress the spring with new or old needles. Granted then all are being set "compressed" but that does change the fuel level in the sense we are measuring "XX" millimeters of float height based on different parameters.

[TopCatGr58]

Here's the diagram from the YAMAHA OEM service manual!



Sure looks like the needle valve pin in compressed to me!

T.C.

[BA80]

It is measured with the weight of the float on the valve, spring compressed. If you doing it any other way it's WRONG.

And it's measured from the highest point of the float (upside down) to the gasket SURFACE, Not the gasket itself.

Read the manual.

[Bonz]

Definitely not disputing if it is compressed or not in the manual.

Just saying that when I look for advice (Factory Pro being one) and want to see how folks who make a living doing this recommend to set it, it isn't with the carbs flat on their back, per se.

The variance in spring tension, float weight, etc is taken out to a large degree when done at an angle, as the point of first contact is not reliant on spring tension or float weight to a large degree.

Don't wanna start an oil thread here, simply pointing out what some recommend as a different way to do float height adjustment.

Yeah, Yamaha is definite in the way they portray the setting of the float height, no question.

[BA80]

The variance in spring tension, float weight, etc is taken out to a large degree when done at an angle, as the point of first contact is not reliant on spring tension or float weight.

Insignificant. Your talking a fraction of a fraction of variance. We're not dealing with a Saturn Rocket, it's a mass produced carburetor.

[motoman]

Here's the diagram from the YAMAHA OEM service manual!



Sure looks like the needle valve pin in compressed to me!

T.C.

That's quite a spread on the millimeter setting of the early carbs. Not the case with the later carbs.......half a millimeter, IIRC.
EPA happy and a PITA on the later carbs.

[BA80]

No wonder y'alls carbs run rich.............

[3Phase]

It's not difficult to prop the carbs up, or simply hold/balance them at the angle where tang touches spring nub and use the other hand to position the float gauge for a reading.

Great! Now all of the floats are at exactly the same height! Where are the fuel levels in the float bowls?

Check the running fuel levels and apply the same due diligence you used to set all eight floats to exactly the same height and count the exact number of turns for the mixture screws.

Personally, I find the angle where it just touches, and manually compress the spring with pressure on the float a few times to get a good look at the point the spring is gonna start to compress. It's easy to "walk it in" and get the float height reading on each carb.

Were you able to successfully set the ride height on your XS by lifting it up, tilting it sideways and then 'walking it in' until the tires barely touch the pavement?

I think everyone blips the floats a couple of times against the needle springs, it's like touching wet paint but there's not really any gray area: the float needle springs will support the floats or they will not support the floats. If a spring is weak or bad, replace the float needle.

Now that you believe all of the floats are going to rise up to the same height in the float bowel and shut off the fuel -- where are the actual fuel levels?

Once the heights are set, you can eyeball them all together and verify they are touching the same amount at the same time. Also sight over the floats, and they should look very uniform in height and alignment.

Great! Now all of the floats are level and at the same height! Where are the fuel levels?

Edit: 3Phase, I have seen the weight of the float compress the spring with new or old needles. Granted then all are being set "compressed" but that does change the fuel level in the sense we are measuring "XX" millimeters of float height based on different parameters.

Oh, really? <skeptical look> And by how much did this XS1100 float compress the float needle spring? </skeptical look> That's exactly why Yamaha ditched the meticulous float height settings and published the dynamic float bowl fuel level check.

Make sure you count the turns on the mixture screws too because the carburetors were set correctly at the factory a few decades ago with a different type of fuel in a spankin' new engine so they should never be tuned, only counted.

.

[BA80]

Check the running fuel levels and apply the same due diligence you used to set all eight floats to exactly the same height and count the exact number of turns for the mixture screws.

[Bonz]

Who all's carbs run rich? Ain't looking at my bike when you say that!

Boys, from the "Genuine Yamaha" service manual, in the supplement section for the 80G/SG:

"Hold the float so the tang is just touching the needle"

It does say to hold the carbs "in an upside down position", and the picture shows that, however it is unmistakeable they verbally want the tang "just touching the needle" and that isn't happening in a full upside down position. Paint by numbers or read the fine print? Order fast food by pictures or by what it says underneath?

IMO, they would not have changed the wording from the original manual and offered this in the supplement if the words weren't to supersede the pictures, as the pictures would have sufficed otherwise and nothing would have changed other than the float height spec itself.

Edit: 3phase, I got a pretty good running bike to show for whatever method or effort I put into doing the carbs... Did you like that sexy tan plug color on top of Pikes Peak? Just having some fun now!

Sure, setting fuel level is the most accurate method... Since it isn't a Saturn rocket, I will stick with less precise rudimentary methods!

I don't know crap compared to you and BA80 in the grand scheme, but this is how a guy learns by discussion.

[stereomind]

carbs are like snowflakes, they're all different you can measure float level while riding a unicycle, with the carbs hanging off a fishing pole strapped to your head, if that's what lets you achieve proper fuel level.


peace

vlad

[3Phase]

I'm having fun too, Bonz, but your XS doesn't even have enough miles on it to be broken in yet so why are you goofin' with the floats and the carbs anyway?

Yes, the 'fine' manual will let you set the mixture screws, float height and for the '81 and '82 carbs, the fuel levels. The engine will start and it will run, usually quite spectacularly but after that is the difference between turn-counting and tuning.

For example: the color of the right-hand muffler outlet on Columbo was always a hair darker than the one on the left, even after I split the cases and did a hone, re-ring, lapped the valves and set the float heights with micrometer, not a caliper. I finally picked up some plastic tubing and four of those 8mm brake bleeder screws to fit in the float bowl drains, then checked the fuel levels in the carbs.

Yep, you got it! The float heights were all dead-accurate and set to precisely 23.0mm +/- 0.0001mm but the running fuel levels were lined up in the tubes like the helmets on the Jamaican Olympic Bobsledding Team running the luge and the guy at the back, #4, was obviously way too high.

Seriously -- set the float heights, button up the carbs, check the running fuel level in the float bowls, synch the carbs and adjust the mixture screws, then leave them alone for a couple of decades and go ride until the float needles and seats wear out and have to be changed.

.