All 2st Needles digits and numbers

When I was researching Yamaha YZ125 vs. Husky CR125, I came across this explaination. This will show the basics of the Mikuni needle code. It's definitely more confusing than the Keihin.

Example of Yamaha YZ125 Needle (6BFY42-74):
6 = Series 6 needle
BFY = Triple tapered: B / F / Y
1st taper = B (30sec = 0.5 deg)
2nd taper = F (1min 30sec = 1.5 deg)
3rd taper = Y (6min 15sec = 6.25 deg)
42 / 43 / 44 = Standard / 0.5 clip Richer / 1 clip Richer
-73 / -74 / -75 = Needle Straight Diameter (OD) = 2.73mm (1 step richer) / 2.74mm (standard) / 2.75mm (1 step leaner)

Example of the Husky CR125 Needle (6DJ8-60):
6 = Series 6 needle
DJ = Double tapered: D / J
1st taper = D (1 min = 1 deg)
2nd taper = J (2 min 30 sec = 2.5 deg)
-59 / -60 / -61 = 2.59mm (1 step richer) / 2.60mm (standard) / 2.61mm (1 step leaner)

The way Mikuni Needle numberings work is:

• The first number is the length series. Lets take the series 4 needle. It could be 40.00-49.99mm in length. In turn a 5 could be 50.00-59.99mm in length.
• The second and sometimes third characters being letters describe the taper from the clip end to the tip in 15 second (1/4th of a degree) increments. For example "B" is 30 seconds, and "E" is 1 degree, 15 seconds. Therefore a "BE" would be a taper starting out at 30 seconds (1/2 degree), followed by a second taper of 1min 15sec.
• The last digit be it one or two characters is the suffix or revision number. Example. 4D3, and 4D8 are the same style needle, similar in length and taper. However the taper may begin higher up on the needle than the other. This would make a smaller tip diameter, or a shorter needle. If shims, or clip positions were incorporated on one needle it is possible that it may effectively perform like the other. For this reason we sometimes suggest ordering a 4D3, or 4D8 for example if an OEM application calls for a 4D5 which is not available, instead of a 4E?
• The numbers following the "-" denote the Major OD and is read as follows. "-60" is equal to 2.60mm OD.
• One last note: A suffix number has the following unknown variables between one needle and another. Exact length, Major OD, Point of begining of taper in reference to clip position. Without physically measuring them there is no way to determine these characteristics just by looking at the part number.

6GAY69-74:
6 = Series 6 needle
GAY = Triple tapered: G / A / Y
1st taper = G (1 min 45 sec = 1.75 deg)
2nd taper = A (15 sec = 0.25 deg)
3rd taper = Y (6 min 15 sec = 6.25 deg)
69 = I'm not sure. See below
-74 = 2.74mm OD

6DEY15-74:
6 = Series 6 needle
DEY= Triple tapered: D / E / Y
1st taper = D (1 min = 1 deg)
2nd taper = E (1 min 15 sec = 1.25 deg)
3rd taper = Y (6 min 15 sec = 6.25 deg)
15 = I'm not sure. See below
-74 = 2.74mm OD

Note:
The 69 vs. 15 is difficult to decode because they could offer different clip positions. You almost have to set the 2 needles next to each other and compare lengths and clip positions.

Based on your two needle codes, it appears the primary difference is the 1st and 2nd tapers. Which should have an effect on the 1/4 to 3/4 throttle range.