The Young Timer

Getting a 420 ready for plow day.

By Tyler Buchheit


            I must admit that my bias for two-cylinder John Deere tractors has been in favor of the horizontal Waterloo built units. I never spent much time around those ‘other’ little John Deere tractors. Those tractors never sounded quite right to me with their small sound to match their small size. I guess my mental association to some childhood experiences with a Ferguson T0-20 made me leery of the John Deere models of similar size and style with regard to their pulling power and braking ability (or lack thereof).

            Since my first Expo trip to Iowa back in 1993, my uncle Dwayne shared with me his interest in those little John Deere models, or Dubuques as he called them. His philosophy for tractor collecting was that it aught to fit on his bumper hitch trailer and be pulled by a half-ton pick-up…thus the Dubuque built Deere tractors fit into his plan quite well. Admittedly, I spent the majority of my tractor expo time at sales and swap meets looking at and listening to the big two cylinder tractors…their thump thump thumping kept my fascination much better than the quiet exhaust tones of the little tractors over which uncle Dwayne was drooling. I remember the big Wheatland tractors like the 80 or 730 really caught my eye since they reminded me of the giant steam locomotives of yesteryear.

            Previously, about the only experience I had with the mechanical working of any Dubuque JD two cylinder tractor was replacing spark plugs and points. Dad farmed with an early John Deere 2440 utility tractor that was assembled in Dubuque…but then we’re not really talking about a comparable era of tractors. I also recall that I once installed a vol tage regulator and a new wiring harness on a 420W equipped with a direction reverser. Well, I also remember splitting a 40T after the clutch linkage fell apart and wasn’t able to be disengaged. I can still remember thinking, at the time, that working on the clutch on my 720 was so much easier.

            With my biased perspective out in the open, we can move onto my first real in-depth experience with a Dubuque built JD two cylinder tractor. In anticipation for attending some local plow days, my uncle Dwayne suggested he might want to plow with one of his ‘little’ tractors and his two-bottom JD plow. His idea was great, but the issue was that his plow was a model 812 with category II hitch hookups. Avoiding any major modification his original JD 812 plow, we decided it best to find the right plow. So, I set out to find an original JD plow matched for the Dubuque built tractor. He suggested that he might like to use his 420W with 5-speed transmission.

            To provide a little history on the 420W, it had been sitting in an un-insulated pole barn and had not been run for at least four years. We tried to start it a few years back and ended up chasing down many different rabbit trails looking for why it would not start. After replacing the ignition system, we finally discovered the main issue was a really rusty carburetor. With the carburetor rebuilt, we gave the 420 another chance to start. This time the tractor sprang to life, running rough, but nonetheless running.

            I managed to locate a 412 JD 2-14” bottom fully integral plow late in the summer. It was completely equipped with matched coulters and moldboard extensions. We got a deal on the plow because it had a busted tail wheel and a broken moldboard. With the plow purchased for my uncle, we were ready to get the 420W in ‘combat ready’ condition for plowing. He hauled the 420 to my shop in Illinois on his way to an auction, and I set out to get the tractor in shape.

            It was nearly a year ago when we last had the 420W running, so as you might imagine, it didn’t run all that well. The tractor ran and drove with the help of a fresh battery; however, the throttle response was very weak, and it didn’t have much power. Someone had previously installed an alternator and switched the electrical system to 12V negative ground, and after checking the ignition coil, I knew that the ignition system had the right power and polarity. I first checked the plugs and wires, noticing that the No. 1 cylinder wasn’t firing. I swapped out the old spark plugs with some fresh ones and it made a huge difference in the little tractor. I tried adjusting the carburetor to no avail as the load needle made no difference in how it ran. The only thing that adjusting the idle needle accomplished was to make it significantly speed up when screwed nearly all the way in. I decided to remove the carburetor for inspection (finding nothing wrong) after several more unsuccessful attempts to properly adjust it. The engine wouldn’t idle smooth at all with a pronounced up and down yo-yo like surge at all speeds. The only time the engine would quit surging was under a load.

            Knowing how many times my Uncle Dwayne’s tractors have ignition problems (from sitting in his tractor shed and a lack of exercise), I convinced him to spring for an electronic ignition kit with a new ignition coil that I ordered from Genesee Products (I’ve installed about a half-dozen of their kits and am always pleased in knowing that if I need assistance they have the technical support since they manufacture the hardware themselves). The kit installation was as usual a snap. The most difficult part was getting the old coil mounting bracket loose and reinstalling the new coil in the right spot (it’s a tight fit in the ignition coil area). In about 40 minutes, the 420W was up and running again with a nifty new ignition. While the ignition kit did improve the starting and eliminated some of the spitting noise, the surging was still there. Hooray for not ever again having to fool with corroded ignition points on the 420!

            I wanted to see if I could figure out the carburetor issue so I could move onto other areas of the tractor that needed attention. The only thing that I could find out of place in the carburetor was that the screen filter on the inlet fitting was partially clogged. After reinstalling the carburetor I determined that the flow of fuel into the carburetor was a full pencil sized stream. Otherwise, the visible parts of the carburetor innards looked great.  I reinstalled the carburetor only to find the same condition of erratic running was still present. My mind switched to thinking that maybe the governor was the culprit. I disconnected the throttle linkage and started the engine. Keeping my hand on the carburetor throttle shaft, I quickly realized it was unlikely that the governor was causing the erratic running because I had to open the throttle when the engine started sputtering but then close the throttle as the engine sped up. It was almost as if the carburetor had a plugged idle circuit.

            At my wits end, I called for professional assistance. Mr. Mike Shelby of Popin John Co. in Piggott, Arkansas, came to mind as he had previously rectified several other carburetor issues for me and was always very helpful. After explaining the symptoms of erratic running to Mike, he suggested I check for incorrectly installed throttle shaft bushings or wear in that area. He explained that sometimes if the throttle shaft bushings are installed with too much ‘gap’ between the barrel and the edge of the bushing, it can essentially create a vacuum leak causing the idle circuit to not function properly. From my previous teardowns, I remembered that the carburetor had a new throttle shaft, but I wasn’t sure if it had been bushed or not.

            After checking out my carburetor, I found it was never bushed and proceeded to drill and install bushings myself. It was somewhat surprising to see that Marvel-Schebler chose not to use replaceable bushings on the throttle shaft in their TSX carburetors, whereas they did on the DTLX models (used on Waterloo built tractors). The procedure was really quite simple with the help of some little brass bushings (I found them at my local New Holland dealer for $.88 cents each…it turned out they normally stock the bushings for older Ford or Ferguson models the utilized a very similar Marvel-Schebler carburetor as the JD 420), a little drilling, and some reaming. I found it easiest to press/drive the bushings until just a little bit protruded into the barrel area of the carburetor, and then used a rat tail file to make the bushing a flush fit to the contour. This ensured that there would be no gap for air to sneak around the throttle disc.

            My hopes were high that the 420W carburetor issues would all be solved by my own novice handiwork; however, my hopes were crushed. Other than making me feel good about a tight throttle shaft, the tractor ran just as it had previously. To add glutton to punishment, when I was tightening up the load needle assembly after removing it for inspection, my overuse of brute strength caught up with me and I twisted it in half! Feeling like a bull in a china shop and at wits end again, I was out of ideas and took the carburetor to Mike at Popin John in Piggott, AR. He said that he would get right to work on the carburetor and that I must be the first person to over tighten the load needle assembly on a Dubuque carburetor (just kidding of course).

            Mike called and left a voicemail on my phone that the carburetor was ready to go and that he found Slime in the Ice Machine. I stopped by a few days later to get the carburetor and to get an explanation of Slime in the Ice Machine. It turned out that the little 420 Marvel-Schebler carburetor wasn’t in all that bad of condition. Knowing my symptoms, Mike knew of several instances before of a plugged up orifice at the bottom of the idle air circuit. He likened it to the ever famous (this Young Timer had never heard of him) investigative reporter from Houston’s Channel 13 Eyewitness News Marvin Zindler. Using some of the best technology of the 21st century, I found out just what Mike was talking about on It turns out that Marvin Zindler, a one-of-a-kind colorful man, was well-known for his reporting on the lack of cleanliness at area food establishments and often cited Slime in the Ice Machine as a reason the health department shut them down.

            Well, slime in the ice machine or in my case, rusty gunk in the carburetor, kept the idle circuit from functioning properly. While I had cleaned the carburetor with a ton of carburetor cleaner, it failed to get the ‘gunk’ or rust completely out of the idle air circuit. After a test run on Mike’s 801 Ford tractor, we deemed the carburetor ‘combat ready.’ As Marvin Zindler would have put it, that carburetor is now certified blue ribbon clean.

            With a fine functioning carburetor, I was now in a better position to get the 420 ready for plowing. When I was getting the governor linkage and surrounding area cleaned up from the last fifty years of grease and grime, I recalled that the fan belt had a little too much slop when running. After consulting the service manual for the adjustment procedure, I was ready for a real fight to fix it. I’ve never before adjusted a fan pulley with an adjustable sheave design. I recall that my brother’s Farmall Super “C” used a similar design, but we never had to adjust it. Surprisingly, the most difficult part of the adjustment procedure was to loosen the lock-screw mechanism. The pulley sheaves weren’t rusted solid as I had feared and moved easily into place. The one trick that the service manual pointed out and proved helpful was that after tightening the sheave an adjusting notch or two, you should turn the engine over a few turns (with the ignition switch in the “off” position). This allowed the belt to be moved out of the pulley sheaves as it would get pinched otherwise.  

            Now that the fan belt was adjusted properly (any the sheave set screw was tight), I reinstalled the air cleaner and carburetor. After the carburetor was all hooked up, I remembered that I had bought a new choke cable that needed to be installed. The old cable was really sticky and instead of a nice pull knob, it had a flat washer somewhat welded on with a square nut. When I had the choke cable installed and working it was time for the moment of truth. Away I went with a smooth running 420 that ran like it got a shot in the arm! With the carburetor issues out of the way, I was free to address some other issues such as draining and flushing the fluids, replacing the temperature gauge, and overhauling the steering mechanism.

            I changed the engine oil and filter in very little time which left me to drain the transmission and hydraulic oils. Being unfamiliar with the Dubuque style of oil fill and drain plugs I managed to find a lubrication diagram for a 420W on to assist my efforts. Getting the drain plugs out proved no problem, but I found that it was truly a nasty job (not that messing with gear lube is ever a clean job). I was quite surprised that to drain the rockshaft (Powr-Trol) system, two 3/8” pipe plugs are to be removed from the housing that allows the oil to just run all over the back of the tractor! The final drive housings were equally as messy as all that oil just drained down over the drawbar frame and lower 3pt draft arms. All said and done, I had a nice mess all over the shop floor.

            Knowing that I wanted only to get the tractor serviced and in shape for plowing, I chose not to flush the transmission or final drives to minimize the risk of causing the old gaskets to leak. To assist with the draining of the final drive housings, I jacked the front of the tractor up and blocked it to sit overnight.  The next morning with all of the oil drained out of the transmission and final drives I went to work filling them with some good old gear lube. The transmission went smooth with my flexible neck funnel, but the final drives weren’t going to be so easy. The fill and drain plugs are inverted hex (fancy term for Allen head) ½ pipe plugs are located flush with the housing. Since my fancy flexible funnel was too large to fit in the ½” pipe thread hole, I had to find another way to get the gear lube in the housing.

            In a perfect world, I would have had the proper funnel or possibly one of those quart bottles of gear lube with a pointed tip cap and a piece of 3/8 rubber hose, however I just improvised using what I had available. In the box of various pipe & hydraulic fittings that I’ve collected over the last few years, you might expect to be able to come up with an adapter for ½” pipe but that didn’t happen. While scratching my head, I remembered I had just replaced the hydraulic hoses on a 3” JD cylinder I rebuilt a few weeks earlier and still had the old hoses laying in my scrap metal bin. I cut one of the hoses about 2’ in length and could thread the fitting end into the final drive. The tricky part was to find something to serve as a funnel. All of my shop funnels were too large (the hose ID was something like 7/16”) and I dared not ask Teresa for use of her cooking utensils. At last I came across an old caulk tube that had dried up and should have been thrown away (Ha…this is one example of a good reason not to throw something away just too quickly). The improvised funnel and hose worked just fine except that 90wt gear lube doesn’t flow all that fast.

            Draining the coolant was a snap with the handy dandy petcock valves on the lower water pipe and on the engine block. How I wish those headstrong Waterloo engineers would have thought to use something similar rather than crummy old ¾” pipe plugs. After draining, flushing, and draining what seemed like an endless stream of rusty looking sludge out of the cooling system, I was finally satisfied and was ready to get to the thermostat. With a broken temp gauge, I had no idea of engine temperature so I decided for only a few bucks more to install a new thermostat. Upon removing the thermostat housing my decision to check out the thermostat proved a good one as there was nothing inside. It was a quick job to clean everything up and get the new thermostat installed.

            While the coolant was drained I installed a new temperature gauge. In an effort to save a few dollars, we opted for a generic aftermarket temp gauge purchased from a seller on eBay. The gauge looked solid enough and even came with an internal light (which I wired up to the dash lamp lead). Yes, I know some of you are cringing at the thought of an aftermarket gauge, however sometimes we just do what we must. While I had the dash lamp off I removed the old burned out 6 volt bulb, cleaned the contact and housing, and installed a new 12V bulb. To my delight the new bulb and temp gauge light worked like a charm.

            After a few minutes of run time the new temperature gauge needle began moving until it almost reached the hot side of the ‘normal’ zone. What a relief to know the thermostat was working as the needle moved back toward the cool side of the normal range. With a few more minutes of running I noticed some smoke coming from around the exhaust manifold/ tapped cover area. I checked it out but nothing was leaking. It appeared that the engine hadn’t been heated up properly to operating temperature in quite some time and now the oil leak/buildup would be able to burn off. It’s no wonder to me that so many of these old tractors foul spark plugs and don’t seem to run just right due to an engine that isn’t allowed to warm up to operating temperature.

            Having noticed my annoyance at a throttle lever which will not stay put, I had ordered new friction discs and steel washer ahead of the project.......

Too read the rest of this article, see the December 2009 issue of Green Magazine.