Hey Pogers does anybody know what size bing belongs on 1977 MC-5 KTM 125 motor specs sure would help.thx Lee...
Lee, I am not sure but it could be a 27.5 Bing and if it is the settings are 135/140 main...40 needle....2.73 idle jet....5 needle....3 needle placment on the clip. I know that this fit the older 125's but I not sure about the 77 mc5. I hope this helps,I don't have any newer specs but if Doug Wilford or Kip Kern see this post they will be able to shed some light on it.
Thomas Carmichael
Lee, I would tend to believe that you are running 30 or 34 mm Bing model 54 on that bike.
Main jet is (or should be) 170 - 180
Needle jet is 322
idling jet 50
needle in 2nd position (from the top)
Air adjustment screw about 1 1/2 turns out.
This should get you close and then you can fine tune it to your area.
Donny Smith