Carby adjusting...

[JustRandy]

40 minutes ago, Mech said:

Not all two-stroke engines have those holes.

That jogged my memory.  The tube is how I know it's a 2-stroke carb.  I remember swapping that too with no luck.

I thought I posted these pics earlier:

 

The 230s and 250s carbs are the same but look how different the 250s needle is.

[Mech]

Yeah Randy.. they are all very critical and carefully chosen.. 

And.. carbies are not junk..  Just the wrong one for the job.

Read the tests we do to check mixtures and settings.. See if anyone(any one qualified) suggests snapping the throttle open as a test.. on the type of carby you have.. If you want to snap the carby open, which is not a good driving technique, then get a pumped carby..

And you see those small holes stacked up on one tube.. that indicates it needs/gets a lot of enrichment as it comes onto the needle, which means it's running lean somewhere else.. slide probably.

Not all acceleration compensation is richening, sometimes they run things rich, and then lean them temporarily or after attaining speed.

[JustRandy]

On 8/10/2022 at 5:01 PM, Mech said:

And.. carbies are not junk..  Just the wrong one for the job.

My opinion is it's junk, designed before CAD existed, and instead of tossed out of production they just relegated it to 2-stroke engines.  Some carbs have design flaws and the existence of those flaws makes them junk because the flaws are not able to be remedied or compensated for without starting over with a new chunk of aluminum and new design.

On 8/10/2022 at 5:01 PM, Mech said:

See if anyone(any one qualified) suggests snapping the throttle open as a test.. on the type of carby you have.. If you want to snap the carby open, which is not a good driving technique, then get a pumped carby..

Over the years I've seen many tutorials recommend snapping the throttle as a test that supersedes blindly lowering the idle speed and readjusting the mixture screw.  All that matters is the performance and as I said before the only reason for a pilot circuit is to generate a strong vacuum to facilitate starting.  So other than that there is nothing fundamentally wrong with idling with the slide a little higher.

I don't care much about qualifications; only results.  If the tutorial produces the results, then they're qualified.

On 8/10/2022 at 5:01 PM, Mech said:

And you see those small holes stacked up on one tube.. that indicates it needs/gets a lot of enrichment as it comes onto the needle, which means it's running lean somewhere else.. slide probably.

I believe those little holes draw in the air from an air jet.  #12 in the pic.

[Mech]

Yeah well you can believe whatever you want Randy, and you are welcome to your opinions.

[JustRandy]

Is Mikuni also welcome to their opinions?  They also believe the little holes are to mix in air, not extra fuel.

The primary needle jet is a straight tube drawing up the fuel while the air comes up through a separate opening around the tube.  The air and fuel are not mixed together in the tube.  I guess it's good enough for 2-strokes.

But with the bleed type the air bubbles into the fuel as it's drawn up the tube.

You're right that it's important for those little holes to be unplugged, but to prevent the carb being too rich, not too lean.

I guess we both learned something lol.  I'll pay more attention to cleaning those holes in the future.

[Mech]

That tube is in a drilling that fills with fuel when the throttle is closed, it fills via the main jet and those small holes. It fills to the level of the fuel in the float bowl. When the throttle is opened, that fuel level in the drilling drops as fuel is drawn back through the small holes. To start with there is some air being drawn through the top small holes and fuel through the lower small holes. The fuel level in the drilling drops until no more fuel is being drawn from the drilling, but only through the main jet, and it's mixed with air from more and more of those small holes as they get uncovered.

That drilling is sometimes referred to as the "acceleration well".

 

You are lucky that I'm a patient man Randy... but I do have my limits.

Just saying....

[Mech]

Try it, do your own experiments, swap the emulsion tube on your bike, see what effect it has..

Remove a tube with a stack of small holes, and replace it with a tube with one big hole further up the tube..  see if they both perform the same.

[JustRandy]

When the engine is not running the well will be filled with fuel as you say, but so long as the air jet (#12 in pic) is passing air then the well will be filled with air.  I suppose the question is at what point the air jet begins to pass air and I'm not sure how we could determine that with any certainty.

The way they worded that suggests that if there is any fuel in the well, it is so quickly evacuated and replaced with air that it's irrelevant.  If it were designed to hold fuel, I think they would have specified that.

13 hours ago, Mech said:

You are lucky that I'm a patient man Randy... but I do have my limits.

Just saying....

Not sure what that's supposed to mean.  You tell me to download a manual, then you suggest the manual is wrong... and because you disagree with the manual you threaten to give me the cold shoulder?

13 hours ago, Mech said:

Try it, do your own experiments, swap the emulsion tube on your bike, see what effect it has..

Obviously I did that or I wouldn't be in possession of both tubes.  I did every conceivable experiment, including plugging the air jet, removing the air jet, swapping with other air jets.  Unfortunately that was over a decade ago and I've forgotten many of the results.  Seems like there was no way to get the bleed type to work properly.

I also have a variety of slides.  I've even filled the cavity of the bottom of slides with JB weld and have ground the cutouts of slides with rotary tools in my experiments.  I left no stone unturned.

When I say there is no way to get that carb to work, I mean practically any combination of slide, needles, needle jets, air jets, main jets that Mikuni offers will not work.  There is something fundamentally wrong with the design of that carb.

[Mech]

In some philosophies they say there are three types of men, the enlightened ones, the ignorant, and those that are willfully ignorant. Of the three, only the willfully ignorant can't be helped.

 

[JustRandy]

40 minutes ago, Mech said:

In some philosophies they say there are three types of men, the enlightened ones, the ignorant, and those that are willfully ignorant. Of the three, only the willfully ignorant can't be helped.

Calling me names because you disagree with a service manual is of no help to anyone, least of all yourself.

You should have just said, "Oh, my bad.  I made an easily understandable mistake."

But you can't say that because you've already touted being an expert on carbs with 50 years under your belt.  How could anyone like that ever admit being wrong?

I'd prefer someone who knew a little less but could admit being wrong to someone who is sure he knows it all because the one who knows how to be wrong will be right eventually while the one who knows it all will be stuck forever clinging to a fallacy for fear of looking dumb.

That is the basic reason why science advances funeral by funeral.  https://en.wikipedia.org/wiki/Planck's_principle

The only sure impediment to truth is the conviction you already have it.