BS34 carb float setting plastic and brass floats

[gggGary]

This is an issue that has caused a lot of guys problems over the years.
The brass float is height setting point is quite plain to see in the manual picture, the plastic float picture?, not so much.
The pic is fuzzy, angled, gray enough that which surface they use for 22mm is not clear.
I've been successfully using the flat part of the float that is the same level as the stainless bracket/tang. not the lower part after the notch that curves down further out. This results in a float that sits roughly parallel to the carb flange when set at 22mm. Some pics of my method, a selection of plastic floats from the bins mostly with factory??? tang bend.
Let the debate rage. Hyde PM'd me with some questions about this so figured a thread is in order.

 

[xjwmx]

Hmmmm. Different. I have been using 5T's picture which measures from the highest point of the rounded part of the float. And it works well for me.
The measurement is from gasket surface w/o gasket, but my gaskets are stuck to that part and are 1mm thick so I measure from the gasket and add 1mm to the measurement.

 

[gggGary]

added a line to 5twins' pic, which surface is he referring to????

 

[gggGary]

Hmmmm. Different. I have been using 5T's picture which measures from the highest point of the rounded part of the float. And it works well for me.
The measurement is from gasket surface w/o gasket, but my gaskets are stuck to that part and are 1mm thick so I measure from the gasket and add 1mm to the measurement.

View attachment 102481

with the gasket on it you would have to SUBTRACT a mm.......
Well I guess that could be read two ways.........
PS got my camera focus setting HAMMERED, note how much better the second and following pic's focus is, VICTORY!

 

[xjwmx]

It's showing the approx correct measurement, about 21-22 mm at the round part. I remember that from other discussion.

With the gasket on you would add a mm to get the reading. It is reading 1 mm less than it would if the ruler wasn't boosted up one mm It's confusing.

 

[gggGary]

This pic from above is from a set of carbs I rebuilt and have ready to install on "period Piece".

I might be able to go first fire on the lift today. Think I will video that event and put my camera where my mouth is. Everything on carbs is stock; jets, settings, except; one small washer under the needles "cure the off idle hesitation mod" and idle air screws preset to 3 turns out, bench synched via eyeball to light. Bike is stock, slightly louder aftermarket mufflers, uni foam on the stock air filter frames. This bike has not been fired since I rescued it from a field via a CL flipper.
Be back later!
PS I think my pic and 5twins' are showing the same float setting.....

 

[5twins]

Yes, it is confusing. To begin with, you're measuring upside down so larger numbers will represent a lower fuel level once the carb is flipped right side up.

My pic shows a plastic float set to about 21mm when measured to the lower rounded part of the float. This was on a guy's straight piped bobber and seemed to work well. The carbs didn't overflow and maybe he needed the added richness for his mods? Unfortunately, he sold the bike shortly after completion to an out-of-state buyer so future follow-ups were not possible. It's too bad because I really wanted to ride that thing, lol.

To be honest, I haven't done too many plastic floats. Gary's measuring point at the upper flat area could very well be correct. I think we need some sight tube checks with the 2 different setting methods to see which puts the fuel level closer to the bowl-body seam.

 

[xjwmx]

This is the post. The pic I posted is the one that was in there before The Great Obliteration. Whether it's right or wrong, it works for me. FWIW, note that the farther from the hinge the measurement was taken the more accurate the measurement would be (vernier effect) That means the highest point of the round area is the most reasonable place to measure.
http://www.xs650.com/threads/carb-rebuilding-question.43786/page-2#post-436683

 

[nj1639]

I've been visiting a set of the bs34's off and on chasing a hanging idle so this is presently relevant.
Plastic floats.....
Try both settings, as in measuring up to the highest rounded point first. Do the fuel line visual measurement by attaching the clear hose to the drain on the bottom of the carb bowl, and holding the fuel line next to the bowl see where the fuel height is.
Now, set the float to the highest flat setting and repeat the clear fuel line visual.
Guess which setting gets the fuel closest to the top of the carb bowl? Uh huh.

All right, the second setting gets you closest to the top of the carb bowl.

 

[5twins]

From what I've seen, the factory plastic floats have a sleeve inside the pivot area and that makes for a nice precise fit on the pivot pin. Many of the aftermarket replacements don't have this sleeve. They are a very loose and sloppy fit on the pivot pin. This can cause problems with their function, making it very erratic. My buddy had some of these and we just couldn't get them to work right all the time. They did work sometimes but randomly the carbs would just start belching fuel. I think the floats were hanging up occasionally because of their sloppy fit.

 

[gggGary]

Fuel heights

bike is on centerstand with some shim under front tire so it's sitting pretty close to "street flat". I need to get that fuel level up yet.
There is a ball bearing in lower chunk of fuel line on the test tube setup, the tee and lower line help the clamp keep the line on the bowl nipple.

 

[gggGary]

Reset floats lets call it 21.3mm from the "upper" flange level.

Could probably go down a bit more 20.5mm ish but this should do for now. My mantra is change one thing at a time So changed the float height, bumped the mains from 132.5 to 137.5 and the pilots from 42.5 to 45, I suspect there are some ignition issues as I sort out this bike. More to follow.

 

[xjwmx]

I need to get that fuel level up yet

Seems to be conflicting information from the factory since 22 mm (especially at the rounds) doesn't pass the tube test. So...no telling which spec is right & perhaps neither is. All bets are off? Every man for himself?

FWIW I have a gut feeling that since the brass floats would be measured from the rounds, the plastic ones would be too, absent some instruction to the contrary... That one photo to me seems to be showing that actually.

 

[weekendrider]

While 5twins and gggGary are using a ruler to measure, which can be read from both sides, giving the height of both bulb and bracket. The manual is using a vernier caliper showing only at one spot, which looks to me to be the bracket. My experience has been much like nj1639's.

 

[xjwmx]

which looks to me to be the bracket.

Still?

 

[gggGary]

I think the gauge setting is considered to be preliminary to checking fuel level via a tube. I think I have aftermarket float valves in these carbs so that could affect float setting.

I'm about certain that period piece's issues are electrical. The timing light is showing non-fires that coincide with audible misfires. Timing is showing quite retarded at idle. Need to verify that TDC agrees with marks.
pic was taken with the engine running at idle. Have replaced coil and plug wires, caps with no change, cleaning connectors, checking pickups, voltage at various connectors, etc now. Pretty sure I have an extra TCI to swap in. Engine seems OK until under load then breaks up, cuts out badly. So the jetting changes are questionable til I get the ignition sorted.

 

[650Skull]

82SJ Yamaha manual - float Measurement points.....

Looking from a technical angle relevant to picture.

Doesn't make engineering sense to measure at a point lower than the top.
from 75 workshop manual

 

[gggGary]

I was putting it back together and doing electrical tests. I had JUST tested the pickup and had perfect 700ohm readings on both at the plug. Then it wouldn't start or fire at all, pulled the LH cover and found this.

Apparently one strand of wire was sufficient for ohm tests but not so much for running well. Unplugging, plugging the connector a few times must have been the last straw. Will be doing a test ride soon, Prolly pulling the carbs to head back towards stock jets a bit. I did have a battery charger on the bike for testing and will have a volt meter on it for the next rides, headlight gets brighter, battery is recent and strong. I have R&R'd the ignition and kill switches. 11.7 at the coil hot. I have a set of aftermarket needles with clips and 4 grooves I may mess with. Since PP is Allison's bike I will check but may leave timing fairly retarded, she's pokey and tends to lug the motor. This was a rough field sitter bike. I got pushed into the test run regime faster than I would have normally done it, for the float debate going on.

On the float heights; I think I've pretty well shown (proved?) the upper float where the metal tang is, is correct to measure from on the foam float BS34's on XS650s 22mm or a bit less would be a good starting point. These floats do sit pretty much level when adjusted and that's mostly true of foam floats I've seen. Funny, while "researching" I found several forums for other brands showing the lower part of the float as "correct" to set height, but none of those photo's were from factory manuals.... Very common to find a PO that attempted to compensate for leaky float valve o-rings by lowering the floats. Often seen on "barn bikes" I buy that were "running when parked" Uh yeah, uh-huh, sure.

 

[gggGary]

Clearances are tight under that cover, a fat O-ring chain didn't help matters. The wire was probably already torn when I got it, perhaps why it was outstanding in it's field when found.

 

[xjwmx]

^Have you discovered an easy method of tang bending from all this? That wire routing, I would push it downward to help it clear the chain and then squeeze that clamp so it can't move back up. I have the little cable zip tied to the big one at a couple of critical points.