Topic: "clear tube" float height method with 657a carbs?

[aperry]

Hi guys,

I'm confused about the float bowl drains on my 657a carbs.  In another thread I read that I should be able to use the "clear tube method", and I should connect the clear tube to the bottom of the overflow tube.  This made no sense to me until someone explained  that by loosening the drain screw on one of these bowls, gas should begin emptying through the overflow tube.  This would mean that the drain screw is actually a valve that would allow gas to enter the overflow tube (through some internal opening  in the tube that I cannot really see).  But I unscrewed one of the drains and gas just started leaking out the bottom of that drain.  Nothing through the overflow tube.  This drain does not have a nipple on it, so I can't connect tubing to the drain itself.  I've only tried this on one carb,

Can anyone clarify this?

A related question:  The tip of my float valve moves a few mm before it engages the internal spring of the valve.  Should the 26mm measurement be taken when this pin is just barely starting to engage the spring, or should it be taken when the pin is hanging at it's lowest point (a few mm below the point at which it engages the spring)?  I can't seem to find a clear answer to this.  Recently I took my bowls off to re-jet, and after removing them it seemed that each bowl was only about half full.

Thanks!
Aaron

[flybox1]

you'll need to wedge the end of a piece of clear tubing into that drain hole, and then turn your fuel on at the tank. all of your bowls will be like this.

if you heat the middle of a 1' section of tubing, while stretching it, you can get it to taper just enough , and cut it in the middle of the tapered area to screw it in the drain hole..

[aperry]

Thanks.  I think I saw your heated tube method in another thread as well.  I was hoping to to avoid that, but it sounds like someone was wrong about the drain screw opening some valve to the overflow tube.

Do you happen to know what size tubing you use for this?  Thanks!

Aaron

[flybox1]

a few bikes do have the drain screw as a valve to the overflow tube.  yours is not one of them.
the tiny stuff...1/8"ID worked fine for me

[aperry]

Cool.  Thanks!

[fmctm1sw]

Someone sells a gizmo that you thread into the drain and it has a clear tube on it.  Ebay perhaps.

[wrenchmuch]

Check your float height with the float tab lightly contacting the needle valve. The plunger shouldn't be depressed. Hold the rack of carbs horizontal with the engine side facing up at about 11 o'clock and the floats to your right.

[lucky]

Do not use the clear tube method to SET your float levels. Set the floats like the books tell you.
This clear tube method can be used
AFTER ....AFTER you set the floats by measuring the float heights!

Just set the floats like the books tell you.

[aperry]

Do not use the clear tube method to SET your float levels. Set the floats like the books tell you.
This clear tube method can be used
AFTER ....AFTER you set the floats by measuring the float heights!

Just set the floats like the books tell you.

I've seen you post this a few times, but I've never fully understood why (unless it's just as simple as "because the shop manual says so".  Are the following true:
1.  The float mechanism is designed to control the fuel level
2.  26mm float measurement using traditional method corresponds to a fuel level 4mm below the top surface of the bowl (I believe HondaMan noted this?)
3.  The clear tube method accurately corresponds to the fuel level

If those are all true then why wouldn't it be just as accurate (or arguably even more accurate) to use the clear tube method?  I have noticed that the whole float mechanism is somewhat flimsy.  The floats can get a bit contorted/twisted, etc.  If the end goal is to accurately set the fuel level, then why wouldn't the clear tube method be more accurate?

This is more of a curiosity question.  As implied by my second question at the top, I have been using (and will continue to use) the 26mm method.  But I would like a "second opinion", hence the clear tube questions.

Thanks,
Aaron

[aperry]

Check your float height with the float tab lightly contacting the needle valve. The plunger shouldn't be depressed. Hold the rack of carbs horizontal with the engine side facing up at about 11 o'clock and the floats to your right.

Thanks.  I've been doing this with carbs installed, which is easy enough to do.  Especially if the pin at the bottom of the valve can just "hang" there, without engaging the spring.

[fmctm1sw]

Here's the thing I was talking about earlier:  http://www.ebay.com/itm/Carb-Float-Level-Tool-Z1-KZ1000-KZ900-KZ-GS-/271027319980?pt=Motorcycles_Parts_Accessories&hash=item3f1a7cb4ac&vxp=mtr

I know I've seen them for Honda if this one isn't the same.

[aperry]

Here's the thing I was talking about earlier:  http://www.ebay.com/itm/Carb-Float-Level-Tool-Z1-KZ1000-KZ900-KZ-GS-/271027319980?pt=Motorcycles_Parts_Accessories&hash=item3f1a7cb4ac&vxp=mtr

I know I've seen them for Honda if this one isn't the same.

Thanks, looks like this will do the trick, provided it's the right size.  I'll do some research.  Thanks for the link!!

Aaron

[flybox1]

Just set the floats like the books tell you.

Let's insert Honda Shop Manual, in place of BOOK. 
Clymer has been wrong on at least one occasion.

[lucky]

Just set the floats like the books tell you.

Let's insert Honda Shop Manual, in place of BOOK. 
Clymer has been wrong on at least one occasion.

The Clymer's book is correct on this issue at least.

Page 125, Illustration #13 bottom of page.
Clear as a bell.

Page 60, Illustration no. 62 top of page Clear as a bell.
READ #7

Does that look like 4mm? Four millimeter is  .157 thousandths.
Slightly over 1/8 inch.

When someone on this forum can adjust a float properly, then
Let the float bowl fill with gas and  remove that float bowl
without the float dropping and adding more gas while you are
carefully lowering the bowl, thus changing the level,
then please tell us how you did that. so we will know what the gas
level really is AFTER the float has been adjusted with a gauge or a measuring device.

[aperry]

I would imagine we could get a proper fuel level measurement quite easily using a properly measured carb. I would probably do it like this:

Temporarily add some kind of vertical strip (paper or something else that would change color if soaked) up the inside of a bowl that would indicate the highest level reached by the fuel.  Attach the empty bowl (with strip), turn on petcock, let bowl fill completely, turn off petcock, empty bowl using the drain and then remove bowl.  Wouldn't the highest level indicated on the strip correspond to the correct fuel level?  Who knows, maybe even a magic marker line would work (if gasoline wipes away the portion of the line below the fuel level).

I am assuming that HondaMan, or whoever arrived at the 4mm fuel level measurement, did it somewhat like that.

By the way, I do have a Clymer's manual, but it's not with me right now.  I'm currently staring at the Honda Shop Manual and it does not show the fuel level, it only shows how to set the height using a gauge.  I do find it interesting that the Clymer manual is deemed "correct" for something debatable like this, but "unreliable" for so many other things!


Edit:  My method above assumes that someone doesn't trust the "clear tube" method as being an accurate indicator of the fuel level inside the bowl.  If we agree that it is accurate (not sure why it wouldn't be), then forget the strip and all that nonsense.  Just get a properly calibrated 26mm carb and use the clear tube to measure where the fuel level is relative to the bowl top surface.  Then you can use that same measurement (4mm or whatever it comes out to) as a guide for any other carb.   Amiright?

[lucky]

Sounds workable. Are you going to do it?

So far no one has.

[aperry]

Sounds workable. Are you going to do it?

So far no one has.

I may try at some point, but I am hoping to avoid removing my carbs anytime soon.  I rebuilt them and put them back on the bike, and the whole project is nearly complete.  I do have pods and a 4-1 with Cherry Bomb right now, so I'm not sure how long I'll be able to go without needing to change the needle clip position.  If that happens then I'll remove the carbs, get a guage, and measure properly.  For now I'm measuring with carbs mounted, which feels a little clumsy.

Took a spin around the block after re-jetting with #123 mains and so far it seems to be running okay.  But I only have 2 miles on it.  Not sure what to expect on a real ride.  And I've never owned a CB before, so I'm also not sure how well it's "really" running. 

[flybox1]

how will you prevent liquid from 'wicking' up higher than the actual level?
more trouble than it might be worth.
set your floats to OEM level.
get$4 in tubing. cut it to fit, shove them in, turn on your gas.
easy as that. and its an accurate visual measurement for what is going on inside your bowl compared to how you set your floats.

[aperry]

how will you prevent liquid from 'wicking' up higher than the actual level?
more trouble than it might be worth.
set your floats to OEM level.
get$4 in tubing. cut it to fit, shove them in, turn on your gas.
easy as that. and its an accurate visual measurement for what is going on inside your bowl compared to how you set your floats.

Well, yeah, certainly I'd need to select the right material.  I mean really anything that doesn't wick and visibly changes when it's wet.  Heck, I could probably dry out the bowl real well, perform the test above, and then see if there's a clear "wet line" where the fuel level was.  Or, we could just use the clear tube to measure a known-good carb, and use that measurement for setting other carbs with the clear tube.

Anyway, the real meaning of my earlier comment/question was this:  If we can establish a known-good measurement for fuel level (not sure why anyone wouldn't trust HondaMan's 4mm measurement?), then wouldn't you expect measurement via clear tube to be more accurate and reliable than the traditional measurement?  It's the "real" fuel level.  Not the fuel level as indicated by a complex dual-float device where the floats are connected and rotating around tiny delicate easily-bent components.  I know we all love these carbs, I'm not trying to disparage them!

[flybox1]

yes.  this method is showing you the REAL level, and that level adequately covers all jets in fuel at any given time.
the 'traditional' method is to set your floats as they say in print and fahgeddaboudit.   if we dont look(clear tube) we can only assume we set floats right, and the number in print was correct.
well, some of us want to be a little more precise   

[Rookster]

You are talking about 2 different measurements.  Setting the float height on the bench is 1 measurement.  Determining the fuel level in the float bowls is a different measurement.  With both methods you are trying to achieve the same thing, the correct fuel level in the float bowl.  There are situations where a properly measured and adjusted float height will not equal the correct fuel level in the float bowl.  Fuel leaking past the closed float needle is one.  A leaking float is another. 

The only issue with trying to set float height with the carb in situ is how much pressure do you apply to the float?  With the carbs off the bike the partial weight of the float determines where it sits and when it is seating the float needle.  Here's my take: if you are trying to set the float height then something is probably not working like you think it should with your carbs or idle or throttle response.  I would get used to pulling the carbs until the bike is set up like you think it should be.  And if your pulling the carbs you might as well set the float height on the bench.

Scott

[aperry]

Scott, sounds like good advice to me.  The bike seems to berunning okay for now so we'll see about pulling the carbs.  I noticed only half full bowls recently on carbs that I messed around with (turns out the be cracked overflow pipes), which prompted this thread. 

Regarding pressure on the valve, yup, that's why I asked the second question up at the top of the thread. 

[scottly]

There are variables that can throw the physical bench test off, such as the strength of the spring in the float needle post, or saturated plastic floats. The clear tube shows the actual level, is relatively easy to do, and doesn't require removal of the float bowls. Who cares what the level in the bowl is when removed? The level will always by lower than what is shown by the clear tube, since the floats are no longer displacing their weight in fuel.

[bollingball]

There are variables that can throw the physical bench test off, such as the strength of the spring in the float needle post, or saturated plastic floats. The clear tube shows the actual level, is relatively easy to do, and doesn't require removal of the float bowls. Who cares what the level in the bowl is when removed? The level will always by lower than what is shown by the clear tube, since the floats are no longer displacing their weight in fuel.

+1 Could not say it any better.
Ken

[brewsky]

I removed a float, let it float in a jar of gas, and marked the gas level on the side.

Then installed, set height to spec, and measured the mark distance from the bowl joint.

Turned out to be about 5mm below the bowl joint. (This measurement is for 78 750 K8, and not nesessarily the same for other carbs)

If you ride the bike with the clear tubes attached, you will notice the level stabilizes and may be different than when parked, engine off, and on the sidestand.

Some of the early Honda shop manuals mention a design value for the distance between the fuel height and the bottom of the carb bore, but I've never found that value listed anywhere.