new carb

[cory eneks]

ok i was running my 48 8n ford tractor it would run for a minute than die.so i went ahead and put a new carburator a new coil and a new distributor cap on.what is the right calaborations for the screws on the carburator,,,when i put it on it looked like to me that it was flooding and i dont know how many turns the screws should get,,,,so could you help me in setting up the screws on the carburator???thanks

 

[G6 at Snook, TX]

2 turns out on the main adjustment screw. Start it run it warm then you need to fine tune it. Each carburetor and tractor marriage is a bit different. I have heard and used two methods to get it just right:

One, once the tractor is at operating temperature (important, plus if you are going to do this right make sure you have a fresh tuneup for the old girl) then you tighten the main adjustment needle until the motor starts to cut out. When the engine stumbles, back it out 1/2 turn and you should be just about spot on. This is done with the motor at about 3/4 throttle.

Two, again at operating temperature, set your idle two turns out initially, then start tightening the main adjustment screw an 1/8 or so at a time. Each time, rev the motor from close to idle to almost wide open when you get the motor to stumble or hesitate when you rev it you have gone too far. Back the main adjustment out a tad (enriching the gas) until it revs without hesitation. Then you are set.

Some will tell you that two turns is optimum, but I disagree. I have three 8ns and each is somewhere between 1 1/2- 1 3/4 turns out from the needle screwed in tight. Each tractor is different.

The idle needle is opposite of the the main adjustment needle. In for rich out for lean. Done at operating temperature, you try to get the motor to idle at 400-475 rpm, real slow, normally this sets somewhere between 1/8-1/2 out.

If this is a new carburetor, good luck because some of the Chinese re-pops are garbage. Some work just fine. Don't be surprised if you fall into the former.

The main needle faces the radiator. The idle needle faces you when you look at your carburetor.

 

[souNdguy]

Wow.. talk about shotgun parts replacement.. I bet the parts selling people positively love you!

Now.. a bit of diagnostics might have save you a ton of money.. but since you are here.. lets see what we can do for you.

1, looks like it was flooding? how? gas running out the air line connection? were you excessively choking it? does it continue to run/drip witht he fuel turned on? if so, the float valve may be stuck.. might be as simple as a piece of debri from manufacturing inthere.. or the flaot is hung onthe carb wall.. or it is mis installed or not set to .025".. etc.

main (big down pointing needle ).. set it at about 1.5 to 2 turns out and try it. the side pointing idle needle, set it about 1 to 1.5.. on the big needle, out to enrich.. it's a fuel needle.. the side small one is an air needle.. thus out to lean.

Ideally.. when you have a running problem, you narrow it down to spark or fuel, and not just replace components of each randomly.

running for a minute and dieing can be a fuel issue, and you can check the drain plug inthe bottom of the carb to see if you have fuel when it dies. if you do, check spark.. if no spark.. after 1m runtime.. I think I'd jumper power to the coil just to make sure it wasn't a switch issue, then I'd check the condensor to see if it was either shorted or open.. if shorted.. the points are likely ok.. if open.. the points may be burnt.

soundguy

 

[Dell (WA)]

Cory.......you've gotten some excellent advice. Use it wisely.

Next time keep yer itchy-twitchy fingers off'n them handy-dandy carb tweek'ums.

Each carb/engine combination is different, thats why there's tweek'ums.

Heres the way I recommend adjusting the Marvel/Schebler carb. Set the down-pointing mainjet to 2-turns and LEAVITT!!! Then I adjust the side-pointing idlemix for maximum idle speed. NOT SMOOTHEST idle, MAX idle, understand??? Then I adjust the behind the carb idle-speed for a SLOOooow 400rpms. (ennythang under 500rpms is probably good) I do the idle-mix -- idle-speed dance at least 3-times. Remember, the side-pointing idlemix is BASSACKWARDS; out for lean; IN for ENRICH. Usually, the idle-mix lands in the 1/4-turn range.

Running for about 1-min is usually clogged UP-INSIDE the fueltank gas filter. Yes, you haffta remove the whole glass thingy to gitt to it. And amazingly enuff, has 'nuttin' to do with yer carb. ......Dell