120NC Carb Modification?
 

Dave
I have a 120NC that runs really really rich on the low end. To get it to idel I have to really crank the regulator screw in. I think that I remember seeing somewhere that a fix for this was to drill out the air bleed hole in throttle body. It makes sense to me since it would lean out the low end. If this is a fix what size do you enlarge the hole to? Thanks

120NC Carb Modification?
 

Drill it out to 1/8"

120NC Carb Modification?
 

Wow, that is quite a bit bigger.

120NC Carb Modification?
 

Dave,

Mine already has a hole in it. Does it come form the factory with an air bleed hole. I am not sure what size it is, but I doesn't look like it is 1/8". Should I drill it out. Mine has the typical "burping" idle now, but doesn't seem to load up like some others. I could use a lower idle if possible.

Thanks for your help.

Mark

120NC Carb Modification?
 

They have about a 2mm hole from the factory. If the idle is still too rich, open it up.

120NC Carb Modification?
 

Dave,
The 1/8 th inch was way to much. Can't get the engine to run decent. I borrowed a buddies throttle body from a new NC and the hole looked to be about 1/16th or slightly larger. I know it is larger then the hole that was in mine originally. Well time to order a new throtle body. By the way with my buddies throttle body my regulator is sitting flush, the motor idles and transistions great.

120NC Carb Modification?
 

Funny, 1/8" always works fine for us. Maybe there is something different about your throttle barrel. The throttle body is the part that the barrel rides in.

120NC Carb Modification?
 

Dave,
After I modified the throttle barrel I put it in. Set the regulator to flush with casing. Started up, let it warm up then set the High speed needle about 300 from max. Then brought it down to idle and it would sit there and hold an 2100 idle for about 10 seconds then speed up approx 500 to 800 rpms. The engine 8 out of 10 times would die when you were going from max throttle to idle. I tried turning the regulator out and resetting the top end. I just could not get it to run reliable. Borrowed my buddies throttle barrel out of his newer NC which had a larger hole then my original. I installed it, set regulator to flush with casing. Started it up, set high needle, brought it to idle, It was a tad rich, 1/4 turn in on regulator and the engine was purring like a kitten. I guess the moral of the story is that I should have started out just slightly enlarging the hole to find where it ran the best. Do you you have any new thorttle barrels in stock for the NC? If so how much? I need to get one so I can give my buddies back. Thanks

120NC Carb Modification?
 

Give service a call at 775-782-4562 weekdays 9 to 5 west coast time. They should have some.