Jet Needle assistance

People suck

It sounds to me lie you need to increase the jet sizes rather than trying to get extra fuel via needle adjustments. I run those jet sizes on my KZ650B1 with a V&H 4-1 exhaust at about 5000 feet altitude and it runs perfectly, but I do run the stock airbox. With POD filters I think you should start with a larger pilot jet and work from there.

If your's so "excellent", how come you don't know the Mikuni calibration basics? ......Sorry if that seems insulting but it was you that showed up wearing a crown asking Mikuni carb tuning 101 questions :woohoo:

Mikuni Needle numbering system works in degrees and minutes. The letters and numbers tell you the tapers and length.
Two needles: 5DL31 / 5CN18 with two tapers [indicated by 2 letters] Two letter indicates 2 tapers.

Both are 5 Series needles [between 50 - 60mm length]
Begin at A, progressing richer toward Z.

First needle is richer at first taper [D is greater than C] or comes after C in alphabet
First needle is leaner at 2nd taper [L is less than N] or comes before N in alphabet

If both used with same needle jet, first needle would deliver a slightly richer fuel curve at part throttle progressing to a slightly leaner curve as throttle is opened [needle comes onto the second taper.

I get what you tried but that's a somewhat unorthodox method. If the needle on the 5th position still leaves you lean in jetting then you're probably better off with the next size richer needle jet. Those are also alpha-numeric is size selection.

Two needle jets, O-6 / P-4
O is leaner than P.
4 is leaner than 6
However a P-4 is significantly richer than an O-6

Generally if your carburetors have an O series needle jet, you would increment numerically within that series rather than jumping straight to a P series needle jet. Example from O-4 to O-6 to richen the mixture in the mid range. You usually have to start again with your clip position after making a needle jet swap to dial in the mixture for optimal.

Today's pump gas is poor when it comes to efficiency. Very common to have to richen mixture on vintage bikes because of the poor fuel quality. You might better put the carburetor together properly [washer position speaking], put the needle in the 5th clip position [full rich] and install 17.5 pilot jets before you go on a needle hunting expedition.

Mikuni

Where the air/fuel mixture is suspected of being too lean or too rich, if not already done, would perform clear tube tests to assure that fuel levels are within spec (before changing jet sizes or jet needle clip positions, or different jet needles, or needle jet sizes).

For instance, in an otherwise "perfect" carb, a too low fuel level may result in a too lean mixture.

The jet needle taper dimensions are most influential throughout the mid-range of throttle positions (where the tapered needle is working in conjunction with the needle jet), and less influential at slightly open throttle (where the pilot circuit has most influence) and also less influential at wide open throttle (where the main jet size has the most influence).

Good Fortune!

I am befuddled. In the OP, all I see is "people suck" and an exploded view of some carburetor parts. Am I having technical problems? Did something get deleted? :huh:

That's the same as I see. Ed

He changed his original post. Bill is communicating with him. Thank you Larry for posting Mikuni America in your post. I had it on my old lap top but didn't save it on chrome. Lots of good info there.
Steve

Not sure I understand why he felt to change his post to an insulting one, when people were trying to help him. I still don't think changing the needles is the solution to that problem, for it to be that weak there has to be some other issues involved. - but after his post I've just realized I don't care about his problem.

One post, didn't get the answer he wanted, "took his ball and went home." He'll get help if he wants it.
Steve