The raptor 125 oem carb has side mount throttle linkage and the PE-28MM carb is top mount linkage. When mounting the PE carb it is nessessary to purchase a cable due to the clearance issue between the top of the carb and the bottom of the gas tank. Aftermarket cable will have a 90 degree bend on the carb side, this will enable you to somewhat clear the gas tank. You may still have to add 1/4" spacer under the rear of the tank.
The differance between the HMF carb and an ebay carb is set-up. HMF carb already comes with correct, needle, slide, pilot and main.
HMF carb comes with the following
Main - 145
Pilot - 35 or 38
slide - #4 cut out - works well
needle - jjj
OEM carb comes with
Main - 125
Pilot - 42
slide - #2 cut out - (runs rich off idle)
needle - I forget, but not jjj
I guess I'm trying to say is ebay carb may be cheeper, but you will end up spending more in the long run.
I will post later the correct cable number to work with the raptor throttle and PE 28 MM carb.
Hope this helps,