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Subject: 51 8N Spittin & Sputterin

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Steve in MO    Posted 07-22-2018 at 03:42:35 [URL] [DELETE]        [Reply] [Email]  
  • 51 8N Spittin & Sputterin
  • Hi all! I have been lurking for a couple of weeks but this is my first post. I am in a quandary as to what the problem is with my '51 8N.

    A little backstory might be nice so here goes. I bought this gem in 2003 to help around the acreage I had just acquired and feel like I got a pretty good deal. It came with a grading blade and a 5' Bush Hog Razorback so it was quite ideal for my needs. The tractor ran great for many years with just minor upkeep, not being needy like some old girls can be. Then came the dark times.

    On day I let her slip in a bit of damp earth and slid to close to a wire fence and before I knew it the wire was caught on the back tire and up came a T-post. SLICE! The T-post wing got the sidewall of the tire pretty good and being short on funds at the time I let the tractor sit. And sit. And sit some more. 2-3 years passed. I did have the forethought to drain the fuel tank though. Nothing good ever came from leaving gas in a tank for an extended period.

    Good times came but the tire was not salvageable and the wheel needed the valve stem hole welded up to fix the degradation in the area. Check! Welding done and new rubber put on.

    Now old girl is a 1951 8N, 12v conversion, side mount distributor. She was always reliable and started right up in the past but this time she was/is being finicky. Before I even turned the key the carb got rebuilt (M-S TSX241B). Full tear down per Don Stewart at Yesterday's Tractors. Soaked in ChemDip carb parts cleaner and all orifices blown out with compressed air. Clean as a whistle and new parts where provided. Idle and power needles set at 1 1/2 turns out from bottom. Float level is questionable (see later in the story). I pulled the sediment bowl and made sure the screens there were clean. The fuel tank got replaced shortly after I bought the tractor and is still good an clean inside - no rust. Fuel flow is good all the way through. 2min 19sec to fill a pint jar with fuel from the carb bowl drain plug. Yes, it is new gas. Check!

    Air cleaner has been torn down and all the dead wasps and ladybugs removed from the oil cup. Screen and all parts cleaned in solvent, reassembled and filled to the fill line with SAE 30 oil. Air tube is clean too. Check!

    6 quarts of SAE 30 oil and a new filter. Check!

    Ignition system mostly all new. New group 35 12v battery, new coil and resistor, new points (gap at .025) and condenser, new cap and rotor, new copper core plug and coil wires, and new Autolite 216 plugs. I have good fat spark from the coil wire to a bolt on the front axle assembly and my spark plug spark tester shows good spark. The distributor shaft seems to be in good shape from casual checking though I have not pulled it out. Check!

    What's with all those details you ask? Well I figured I would get them out of the way before you go asking later for them and save us all a little time.

    She starts and idles fine though the idle is more around 800rpm not the 400ish it should be. The idle speed adjust is just making contact with the pin and the idle mixture screw really makes no change. But the problem lies when I ramp up the power. I get no real reaction thru the quadrant until I get to the top and then the RPM's come up and it starts spitting and sputtering like the wife got a bug in her mouth! The proof meter is telling me I have the RPM's for the PTO (just barely but nothing more) and the Bush Hog spins up and will cut a bit (nothing heavy) but the tractor just spits and sputters through the field (PTO on OR off) and has the horses looking at me funny.

    I have tried adjusting the Power Mixture in the field, a little at a time (in or out) and then running a bit under load to see if there is any change. No change. I have considered fuel starvation and tried adjusting the float level a bit. No change. I changed the Float Needle Valve to an older steel part from the brass with black tip one. No change. I have NOT messed with the governor or throttle rods or even the governor springs yet but I am considering it.

    Before the dark times the engine ran good but would intermittently surge the RPM's a little and I could watch the governor arms move a bit during that surge. Now the governor arms move a bit but the thing just spits and sputters in the power range and wont come up to full power. Should I maybe try new governor springs or even a full rebuild on the governor? Could the governor be the root cause of my issue? I have never messed with one before but if I can rebuild a GM 4L60E transmission (and get it right) I think I can do the governor. Maybe.

    Carb settings? Governor? Timing? A Colt .45 to the radiator? I am open to ideas and suggestions.

    Steve in MO    Posted 07-22-2018 at 17:55:09 [URL] [DELETE]        [Reply] [Email]  
  • Re: 51 8N Spittin & Sputterin
  • Well I went and tinkered with Ol' Girl today after work and I just gotta say.....Thank You All for your words of advice! At the present moment sitting still with the only load being a spinning bush hog and a gentle summer breeze I am getting good smooth RPM's all through the range up to a bouncy 18-1900rpm which is plenty for my needs, though manipulating the outer lever on the governor it will push up past 2100. The spit and sputter is gone it seems (yes it did it parked too) but I will get it out in a field tomorrow for a better test. Other chores are taking priority today.

    Again, thanks to all.

    R Geiger. Yes the firing order was 1243 but it never hurts to check again. Starting idle hits about 650rpm but after running it up to full throttle and back down the idle wont drop below 850rpm. Not a deal breaker but kinda odd to me. And I found the governor link rod out of adjustment. Per Fig FO58, pg 43, I&T Ford Shop Manual the rod should pull the governor lever to the stop. It didn't but it does now.

    Rustyal. You theory that there was a clog in the carb seems to have been spot on. I tore it down again and while I couldn't find a wire small enough to make those tight turns I did use healthy amounts of carb cleaner sprayed both directions through all the passages and then followed that with compressed air. If there was anything lodged in a jet it is no onger there as evidenced by the much smoother running of the engine. But I've now compressed that carb body gasket 3-4 times now. I must make a mental note to grab another one soon.

    Tim Daley(MI). Thanks for the welcome to N-series tractors but I'm not exactly new. I bought this beauty 15 years ago but it confounded me this time and the shop manuals were not answering my questions. Per the 12v conversion, it was done at some point before I acquired the tractor (so more than 15yrs ago) and has served me and the machine well. I have renewed frayed wiring and the like but have followed what was already there with no deviations, though I am considering actually wiring up all the lights in the future (they were cut at some point). I will keep your advice on the needle settings in mind if I run into any problems. I have read many variations on the theme (factory = 1 turn, Guy #1 = 1 1/2 turns, Guy #2 = 2 1/2 turns, etc etc) but what gets the tractor to run right is the winner.

    Again, thanks to all for their time. Maybe if I lurk here long enough I may be able to offer my own advice to someone and help them out.

    Tim Daley(MI)    Posted 07-23-2018 at 06:43:40 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 51 8N Spittin & Sputterin
  • Just need to cover the basics, and all the bases. Why do say that you need to pickup another carb now? Your original Marvel-Schebler carb is the best thing since sliced bread. Todays' aftermarket ones are mostly Cheena made junky clones manufactured poorly. You had the right idea to remove and rebuild it. The trick is to let it soak for several days at least, in carb cleaner before cleaning out passages. I prefer lacquer thinner myself, shellac thinner equally as well. I use old guitar string pieces for the small orifices. The round wound type add a bit of reaming action to actually 'scrape' the walls to help remove any caked on residue. Simply soaking for a few hours won't allow the cleaner to work at 100% effectiveness. Also, never use drills or reamers to open up passages. It's your tractor, your $$$, so do what you feel is right. As I said, when you ask, you will get standard generic answers, especially when all info not given initially.

    Tim Daley(MI)

    Steve in MO    Posted 07-23-2018 at 07:13:50 [URL] [DELETE]        [Reply] [Email]  
  • Re: 51 8N Spittin & Sputterin
  • I'm not replacing the carb, just the gasket between the two halves to avoid a vacuum leak since I've compressed the current gasket multiple times now doing float adjustments and passage cleanouts. It just seems prudent.

    Guitar string is a good idea. I may pull my old git-fiddle out of the closet and pillage a string off of it next time I do a rebuild/cleanout. Thanks!

    Rustyal    Posted 07-22-2018 at 12:29:28 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 51 8N Spittin & Sputterin
  • The adjusting screw on the carburetor does not make a difference? Hmm. Run a small wire thru every hole in the carburetor. You have a clog.

    R Geiger    Posted 07-22-2018 at 09:30:31 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 51 8N Spittin & Sputterin
  • Did it run this way before you did all the work? If you never ran it before replacing all of the parts, you might double check the firing order. 1,2,4,3.

    R Geiger    Posted 07-22-2018 at 09:26:49 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 51 8N Spittin & Sputterin
  • sitting that long, I would not rule out the mechanical advance in the distributor sticking or maybe some valves sticking.

    The Idle rpm is not a big problem, it is probably sucking air in around the throttle butterfly shaft. 400 is for show tractors, mine seldom run at an idle and one is about 600 and the other maybe 500.

    I don't think the governor is your problem, but disconnect the rod going to the carb and run it up by hand and see what happens, bet it runs the same.

    on the carb adjust, I like to start at 2 1/2 turns out on main jet and with it running full throttle after warming up, I adjust it in until it just starts to falter, then back out 1/4 turn or so. fine tune from there under load.

    good luck

    Tim Daley(MI)    Posted 07-22-2018 at 05:12:11 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 51 8N Spittin & Sputterin
  • Welcome to the wonderful world of Vintage FORD N-Series Tractors -you're gonna have fun! You gave us a very thorough list of many crucial items and what you did. You don't have to go to YTMAG -we have a ton of free info in our HOW-TO's forum, including Don Stewarts carb overhaul. Your carb issues might be solved by understanding how the N engines work. With the updraft fuel system on the carb after rebuild, make initial settings -MAIN JET OUT 1-1/2 turns and leave it. The throttle plate idle screw is set at rebuild 1-1/4 turns off stop post, or so it is just starting to open plate, and leave it. Next, adjust side pointing idle air mix screw to fastest idle, not the smoothest, and start at 1 turn out from full set seat. Note that OUT is for LEAN and IN is for RICH. The key to this is to first; perform when engine is up to operating hot temperature so run it for at least 15 minutes before making any adjustments. Secondly, adjustments arenít done simply by turning one or the other screws once and leaving it. It usually takes 2, 3, or more tries to get it right, with at least 15 minutes between tests. Note where each screw setting is before making a turn and then only go 1/8 of a turn at a time. Adjust a screw, then WAIT! It will take the engine a few seconds or longer for speed to catch up. Since you have a later 8N, you can use your Proofmeter to identify engine RPMSs exactly. Adjust the throttle Ėbehind the carb idle screw for very slow RPMs, 400 is spec. Adjust air idle screw until RPM increases. Then adjust throttle screw to 400 RPMs or til engine almost stops. You can take hold of the rod between carb and gov and shake it and slightly twist it so it isnít being hung and prevents the adjustment cam from moving. Iíd hold of on removing the governor for now, it may be fine, but no need to introduce another factor in the equation until you know for sure. Next, you say you dia 12V switch over job. Thatís fine, but was it done correctly? Check out WIRING PICTOGRAMS by JMORĒ in our HOW-TOíS/ELECTRICAL see LINK below. Download a copy and keep it handy. Verify your wiring matches one of the set ups JMOR documented. 99.98% of non-starting/non-running/poor running issues are due to incorrect wiring jobs whether 6V/POS GRN or 12V/NEG GRN. Many supposed fuel issues often are electrical issues vice versa. You donít go into your electrical at all so check it out completely Ėno deviations from the pictograms allowed.

    Tim Daley(MI)

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