zuhnc
Member
- Location
- Macks Creek, MO
I have two TSX-241-B carburetors, one from each of my 8N's. The current in-service one is running rich, as evidenced by soot on the spark plugs. Jets were replaced per recommendations of JMOR, HOBO, and others. 0.032" idle jet, 0.046" main jet, and 0.046" economizer jet. Main nozzle has to be about 4 turns out to even get to run; at three turns out won't even start, much less run. The idle nozzle has limited effect on idle, most noticible between 0 and 1 turn out. (Yes, I know IN for rich and OUT for lean.)
I have disassembled both the in-service carb (we will call this one the "new" carb) and the not-so-clean one on the being-rebuilt 8N (we will call this one the "old" carb). I have noticed two differences, other than the jetting (not pertinent at this time). The pointy end of the main adjusting needle on the new carb is not as tapered as on the old. The second difference is, with the new carb, the needle goes into the little brass bushing at the bottom end all the way to the shoulder, and with the old carb, the needle stops about 90% of the way up the taper.
The question is: should the needle go all the way into the bushing, or should the taper seat on that bushing. Since the needle goes all the way up to the shoulder on the new carb, I think this is why that needle needs to be 4 turns out; at that point the taper is starting to control fuel flow.
Here are some images of the old and new needles, and close-ups of how the needle fits into the brass bushing.
Needle overall
Tapered end
Bushing in new carb
Bushing in old carb
Definite difference in size.
Needle in new carb bushing - needle goes into shoulder on straight portion
Needle in old carb bushing - needle is still on taper prior to straight portion
Close-up - needle in old carb bushing; seating on taper
Close-up - needle in new carb bushing; seating on shoulder, straight portion inside bushing
Any thoughts on correcting this? I can swap carburetors, but that still leaves the issue for the other tractor engine. zuhnc
I have disassembled both the in-service carb (we will call this one the "new" carb) and the not-so-clean one on the being-rebuilt 8N (we will call this one the "old" carb). I have noticed two differences, other than the jetting (not pertinent at this time). The pointy end of the main adjusting needle on the new carb is not as tapered as on the old. The second difference is, with the new carb, the needle goes into the little brass bushing at the bottom end all the way to the shoulder, and with the old carb, the needle stops about 90% of the way up the taper.
The question is: should the needle go all the way into the bushing, or should the taper seat on that bushing. Since the needle goes all the way up to the shoulder on the new carb, I think this is why that needle needs to be 4 turns out; at that point the taper is starting to control fuel flow.
Here are some images of the old and new needles, and close-ups of how the needle fits into the brass bushing.
Needle overall
Tapered end
Bushing in new carb
Bushing in old carb
Definite difference in size.
Needle in new carb bushing - needle goes into shoulder on straight portion
Needle in old carb bushing - needle is still on taper prior to straight portion
Close-up - needle in old carb bushing; seating on taper
Close-up - needle in new carb bushing; seating on shoulder, straight portion inside bushing
Any thoughts on correcting this? I can swap carburetors, but that still leaves the issue for the other tractor engine. zuhnc