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Subject: Carb Tuning?

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Tom S.    Posted 06-11-2020 at 11:49:50 [URL] [DELETE]        [Reply] [Email]  
  • Carb Tuning?
  • I have a 49 8N with a replacement M/S carb I installed in 2018. Over the past couple of years it's ran pretty well (some hiccuping at lower RPMs, but has had plenty of power so I left it alone). But it became increasingly hard to start this winter and spring, so I just installed new plugs, points, distributor cap, and coil (it's 6 volt). Having done that, it starts like a dream, but it runs quite rough and only seems happy if I keep the choke pulled about halfway out. Then it runs very smoothly at all rpms.

    I was wondering if the new electrical means I need to readjust the carburetor, or is there something I might have missed in the electrical work?

    Thanks.

    Tim Daley(MI)    Posted 06-12-2020 at 05:51:47 [URL] [DELETE]        [Reply] [Email]  
  • Re: Carb Tuning?
  • "I was wondering if the new electrical means I need to readjust the carburetor, or is there something I might have missed in the electrical work?" -not usually. Fuel and spark are two different items. A '49 tells me it is a front mount distributor. Having a 6V battery dos not mean that it is wired correctly for the 6V/POS GRN electrical system. A tune-up never hurts; OEM Manual suggests points get dressed at least once a year, but need to concentrate on one issue at a time which sounds to me like a fuel issue. Just swapping an out-of-the box carb, especially a new aftermarket one, without verifying proper settings, is rarely going to work right. Back to the electrics -get setup right first -spark test, wiring, etc. Verify wiring is correct per manuals and JMOR's Pictograms. When you changed the points, did you set the gap to .015" per manuals and set the timing correctly? Was distributor mounted correctly after rebuild and re-mounting? Get it off 180 and you bust the aluminum base and render it useless. You can get distributor bench tested from Bruce(VA)'s 75 Tips. Battery needs a full charge under load - have it tested. Wiring includes the 3-Wire/3-Brush 11 AMP B-Circuit Generator; Voltage Regulator; OEM Ballast Resistor; Coil; Ignition Switch; AMMETER; 3-Wire Starter Motor w/Solenoid; and all wired correctly. Lights were optional accessories so take out of equation for testing, can add later. I also rebuild front mounts. Do you have the Essential Manuals? Diagrams for the carb and distributor are in both. If not, here is a sample. Sometimes you need to adjust the governor but a new carb or a rebuild carb may need slight tweaking. Do the fuel flow test first. Get carb and fuel set correctly first. Do you have your original Marvel-Schebler TSX-241 carb? If so, I can rebuild it for you -email is open.

    FORD 8N TRACTOR WIRING DIAGRAMS:




    CORRECT FORD 8N ELECTRICAL SYSTEMS - 6V & 12V:

    *PICTOGRAMS courtesy of JMOR

    FORD FRONT MOUNT DISTRIBUTOR WHAT HAPPENS WHEN MOUNTED 180 OFF:

    FRONT MOUNT TIMING PROCEDURE:

    FIRING ORDER, 1,2,4,3 CCW:

    FORD N-SERIES CARB & ADJUSTMENTS:










    FORD 8N TRACTOR ESSENTIAL OWNER/OPERATOR/PARTS/SERVICE MANUALS:

    Tim Daley(MI)


    Tom S.    Posted 06-12-2020 at 12:42:59 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Carb Tuning?
  • Thanks for all the information! I do have the IT Manual, but not the others. I think I did a pretty good job setting the new points and testing the distributor for continuity, but this gives me more stuff to try this weekend.

    That rebuilt carburetor is a thing of beauty.

    K.LaRue-VA    Posted 06-11-2020 at 12:11:34 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Carb Tuning?
  • When was the last time electrical connections were made clean and shiny? Especially both ends of both battery cables and both ends of each wire from the battery connection at the solenoid, to terminal block, ignition switch, resistor, and coil. The ignition switch itself can become a resistor. The ignition resistor can get so old it does the job too well. If all those are corroded, rusty and dirty the engine eventually barely runs if it will even start.

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