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I was given some older sleds, a John Deere JDX6, a Yamaha SW433,an older Polaris 340 with dual carbs (seized), and a 340 SkiDoo. My question is on the John Deere, It has a Walbro Carb and a CCW motor. I drained and cleaned the fuel tank and put on new fuel lines and filter. I also put in a new diaphram kit in the carb. There is lots of spark. The only way to get it running is to use the priming bulb untill the carb is soaked with fuel and then keep priming while pulling. When i get it running, and if I can keep it running for a bit, it will take off and run like a wildcat for 5 min or so. Then if it stalls, I have to prime it while pulling to try and get it running again. The guy I got it off of said they could get it running, would run great for awhile then not. He said his problem was the points getting out of line, but they seem fine, and if i pull the motor over like crazy, usually one plug is wet and the other is not, but lots of spark on both. I did not remove the pulse line, but it visually looks OK, it is a rubber line. When it does run, it smokes pretty bad even though i made an error in fuel mixture and did 50:1 instead of 20:1 . If I can master the problems on one snow machine, hopefully it will help me on the others. Thanks
Answer -
Hello Rich,
Sounds like you have acquired a good set of sleds. Usually this problem stems from a combination of the spark plugs not firing well under compression, and the fuel system. Here is what I recommend. Try a fresh set of NGK B7ES spark plugs, gapped at 0.025 in. This should help immensely. Other than that, make sure the fan belt is in good shape, and turning the fan. Those carbs really don't like to go good, unless they are soaked in solvent over night and blown out with compressed air. You can use things like kerosene or STP concentrated fuel system cleaner to soak it. Also, using cheap oil such as TCW-3 or oil that is only NNMA certified can lead to these types of problems. Try using Amsoil or something of that quality. If you continue to experience these problems, try a jet one size smaller. I think with good plugs, a carb soaking, and quality oil, you won't be able to stop the Deere. The Deere's do have a problem like many older sleds with the coils getting weaker with age, so you may want to replace it in the future. Here is a good Deere site that may interest you: http://www.angelfire.com/pa2/jdsleds/ . You can find a few parts at www.mfgsupply.com , www.denniskirk.com , and www.alssnowmo.com . Let me know if you run into any trouble, or need any help with the other sleds. Good luck with the sleds, and happy trails! --Arcticatman
I've cleaned the carb again and got new plugs and here's what happened.
I forgot what # of plugs so I asked at Can Tire and got #9 plugs instead of #7. I set the points and plugs after cleaning the carb and the machine started fairly easy. Ran it around the yard a bit and then shut it off. Could not get it started again that day. A couple weeks later, tried again. The #1 plug was not working anymore at all. Got a new set of #9 plugs and the machine started ok. I ran it for 2 miles and it went really good, then it started missing and i got back to the yard before it quit. #1 plug was dead again. Got another set of plugs this time the #7's (I thought I was doing better with the #9's but found out the 7's are hotter than the 9's). Put them in and could not get it to fire, but there was lots of fuel in the carb, plugs were not overly wet though. Tried again a few days later, still would not fire. I then reset the points, made sure the plugs were good and clean and it started ok. Ran about 2 miles again like a scared rabbit then clunk, it just died. Pulled the plugs, both looked ok, light tan color, and looked like both were firing. Cleaned the plugs, reset the points and i got it to fire then stall and it would not start again. The guy I got it off of said that was his problem, they would work on it and it would run good for a short period then die, over and over again. He reset the points each time, but even though I've been doing that, the points still looked gapped ok. I priced out coils, $25 each, but I don't want to spend money on that if there are other problems. It's strange that it is only a 1.5 to 2 mile machine each time. Thanks.
Answer -
Hello Rich,
Sorry the Deere is giving you a hard time. Here is what I would recommend. I understand not your not wanting to spend money on coils if that is not the problem with the sled. When the sled goes dead after a 2 mile ride, pull the plugs right away, and check them for spark. This is a good way to tell if the coils are failing. If there is no spark or a weak yellow-orange one, then you will know they need replacement. One other thing you may wan to check is the compression, as that could cause this type of problem. Let me know if you have any success, or any questions at all. Good luck with the sled! --Arcticatman
Thank you so much for all your help, it is greatly appreciated. I found out yesterday why it just went dead instantly this last time, the pulse line came out of the carb. Got that fixed, poured some fuel directly in the cylinders, and a little in the carb. The machine took right off and ran great for a mile or so then it lost all power and slowly quit. Pulled both plugs, #1 was cold and wet, but when I checked for spark it looked ok. #2 was hot and dry, good spark as well. To this point it has always been #1 plug. Let the machine sit for 5 min or so, swapped the plugs to opposite sides, poured some fuel in directly and away it went, for about 1/4 mile then died again. I let it sit for a couple hours, cleaned both plugs good, checked for spark and both were really good, poured some fuel in directly (this just seems to give an instant start) and away it went. It was running and moving but powerless, so while running I grabbed the wire off the #2 plug which made the machine run no different, but when I accidently touched the wire instead of the boot, I got a good shock. The plug was cold. This was the first time I had trouble with #2 cylinder dying as each time before it was #1. I plan on trying to check the compression (it is fairly tough to pull the motor over though)Can I loose the compression after it warms up and thats when The one plug gets wet and dies even though there is current going to it. There is some leaks around the motor you can see oil. I suppose if I pull the motor off and rebuild it then go through everything one step at a time I would have a machine good for years. One other question is if I work on these machines in the summer, is there harm I will do to the motors running them when it is that hot out?
Thanks again.
AnswerHello Rich,
Glad you were able to narrow things down to an extent. What it sounds like, is it runs too rich, and is fouling the plugs when it is running. When the sled dwarfs up, parts expand, and the gaskets can leak if they are worn. When they leak, they allow the pressurized charge of fuel and air to leak slightly, and they also can allow air to enter the engine. My recommendation would be to install new piston rings, crank seals, and gaskets. As expensive as some parts manufacturers try to make it look, older engines can actually be rebuilt quite cheaply, would good results. Here are two companies that sell rebuild parts for the Deere:
DENNIS KIRK:
http://www.denniskirk.com/jsp/product_catalog/mmy.jsp;jsessionid=CPYCJGU3OPGGXLA
MFG SUPPLY: www.mfgsupply.com
Basically you will only need new rings, needle cage bearings, a full complete engine gasket set, and new seals which are generally included in the gasket sets. Other than that you may want to replace the pistons, wrist pins, bearings, and circlips.
Here are some tips for a rebuild job, that you may find helpful.
INTRO:
Rebuilding the lower end of a two-stroke engine is the procedure that is most often put off until next race/month/season. When you start hearing the engine make a strange knocking sound, it's time to shut it off and tear it down rather than pin the throttle wide open and hope it will just go away! While rebuilding the lower end you should replace the ball bearings that support the crankshaft and the transmission shafts, plus the rubber seals. In most cases, the crankshaft will need to have a new connecting rod, pin, bearing, and thrust washers installed. Although some aspects of lower end rebuilding are very specific to a particular model engine, this section gives you an overview of the general process.
THE RIGHT TOOLS
Engine rebuilding is nearly impossible without the right tools. Some guys try to use the “caveman” method—big hammers and chisels. As a result, they usually do some stupid thing that ruins expensive engine components.
To properly rebuild your lower end, you will need the following tools from the manufacturer: a service manual for torque specs and disassembly/assembly techniques specific to your model engine, a flywheel puller, a clutch-hub holder, a crankcase splitting tool, and a crankshaft installation tool—but I'll show you how techniques for removing the clutch and installing the crank so you can save money on those tools. You will also need an air- or electric-powered impact wrench to remove the nuts that retain the flywheel, clutch, countershaft sprocket, and primary gear; a parts washer with solvent to clean the engine parts; a hydraulic press to remove and install the bearings because a hammer will only damage them; a propane torch to heat and expand the aluminum crankcases to remove or install the bearings because they have an interference fit (meaning that the bearing is a slightly larger diameter than the hole that it fits into); a digital caliper to measure certain engine parts and compare them to the minimum wear specs listed in the service manual; a variety of tools such as wrenches and sockets; and soft tools such as brake cleaner, thread locking agent, penetrating oil, seal grease, and gasket sealer. A simple way to hold the engine while you work on it is to make an open square box from wood blocks. A universal box for any engine can be made from 2´4-inch blocks with the dimensions of the box being 5´10 inches. CC Specialty makes a ball-vise for $100 that is convenient if you plan to rebuild engines frequently. To permanently remove the temptation to use steel hammers when rebuilding engines, buy a plastic mallet. Snap-On makes a lead-filled plastic mallet that works excellent. The last thing you will need to rebuild an engine is several parts storage bins. I prefer to separate the engine's components into separate bins—top-end parts, electrical parts, clutch parts, shifter parts, transmission, and crankcase bolts. This enables me to keep the parts organized for quick assembly. I also puncture small holes in the bottom of the bin so I can pour parts cleaning solvent into the bins to clean the parts. Then there isn't any chance of the parts becoming lost in the bottom of the parts-washing tank.
TOP END DISASSEMBLY AND INSPECTION
Refer to the sections on top-end rebuilding and exhaust valve servicing for more information on this topic.
ELECTRICAL SYSTEM DISASSEMBLY AND INSPECTION
Use an impact wrench to remove the flywheel nut. Don't be tempted to jam a screwdriver in through one of the holes in the flywheel to prevent it from spinning. That will damage the coils under the flywheel. K&N makes a threaded flywheel puller that has left-hand threads to fasten to the flywheel and a right-hand-threaded bolt to push on the crankshaft. Put a dab of grease on the flywheel end to prevent the bolt from galling and damaging the machined center on the crankshaft end (if the center is damaged, it is much more difficult for a technician to true the crank). It's OK to tap on the end of the tightly threaded puller with a plastic mallet.
Here is a tip for removing stuck flywheels. Use a propane torch to heat the center hub of the flywheel. Take care not to shoot the flame through the holes in the flywheel. Then spray penetrating between the crankshaft end and the flywheel. This should loosen the flywheel enough for the puller to pop it off.
When the flywheel comes off, inspect the center-hub rivets and look for tiny cracks in the hub around the rivets. Replace the flywheel if there are any cracks. Big-bore bikes may have problems with shearing flywheel Woodruff keys, especially on the KX500 and YZ490. The problem is that the flywheel is not matched to the crank at the taper, but that can be corrected, using the following procedure. Remove the Woodruff key and apply grinding paste to the crank's taper. Hands press the flywheel onto the crank and turn it back and forth for five minutes. This will hone down the high spots on the surfaces of each part so the flywheel won't ever loosen up and shear the Woodruff key. After matching, clean the parts thoroughly with contact cleaner.
SPLITTING THE CRANKCASES
Remove all the case bolts, and install the case-splitting tool on to the left-side crankcase. The puller's two bolts thread into the stator-plate mounts. The center bolt of the puller threads up against the crankshaft end. Apply some grease to the end of the crankshaft so the puller's tapered bolt doesn't gall the end of the crankshaft. Slowly tighten the puller bolt and tap around the outside of the cases with a plastic mallet. This will help break the bond of the case alignment pins. If the cases start to split apart with an uneven gap from front to rear, then tap on a part of the right-side crankcase with a plastic mallet. You may also have to tap on the countershaft, but be careful because you could break the bearing support ring that is cast into the case.
To remove the transmission shafts, you need to first remove the shift forks. Pull the rods that hold the forks, and then pull out the forks. Place the forks onto the rods, and set them in a parts bin in the order that they fit in the engine. The rod with the outside of the right countershaft bearing is very vulnerable on Hondas. Pay attention to the placement of shims on the ends of the transmission shafts; sometimes they will stick to the bearings and fall out later when you are washing the cases.
CRANKSHAFT REMOVAL AND INSPECTION
Sometimes, the crank will be difficult to remove from the right-side main bearing (on all engines except Suzukis). Never strike the end of the crank will a metal hammer; try a plastic mallet first. If that doesn't work, then thread the primary-gear nut on to protect the threads and use a hydraulic press to remove the crank. Measure the rod clearance to determine if it needs to be rebuilt. Check the crankshaft run-out and true it if necessary before installation. See the section on crankshaft repair if your inspection reveals a problem.
BEARING REMOVAL AND INSTALLATION
The best way to remove or install bearings is by heating the aluminum crankcases with a propane torch, and then using a hydraulic press to gently push them out. Never pound the bearings out with a hammer and punch. The outer race of the bearing is the only part of the bearing where a press slug should be placed. Large sockets or discs work well as press slugs. Placing the new bearings in the freezer for two hours and heating the cases with the torch will enable you to install the bearings without a press. Fit the bearings into position with as little stress as possible exerted on the crank ends. Some manufacturers make special tools that wedge in between the flyweights so you can press the crank into place (Kawasaki). Other manufacturers use a threaded tool that draws the crank into the bearing.
CRANKSHAFT INSTALLATION
Here is a simple way to install the crank. Place the crank in a freezer for two hours so it contracts in size. Get a cylindrical piece of aluminum with the same diameter as the inner bearing race. Heat and expand the bearing's inner race by heating the aluminum slug with a propane torch for five minutes while it rests on the inner race of the right-side main bearing. Drop the cold crank into the hot right main bearing Now repeat the procedure for the left main bearing, and prepare to assemble the cases.
ASSEMBLING THE CRANKCASES
With the crank and transmission fitted into the right crankcase, you're ready to assemble the cases. Kawasaki and Yamaha use non-drying sealer as a center gasket between the crankcases. Apply the sealer to one side of the case. Spread it evenly with a business card and let it set-up for about 10 minutes. Next, place the left case over the crank and transmission cases, press the cases toward each other to within 5mm of sealing, install the bolts that fasten the cases together, and slowly tighten them while maintaining an equal gap between the cases. You may need to tap the case lightly because you are trying to align eight different cylindrical pieces all together (crank, transmission shafts, shift-fork rods, shift drum, and case alignment pins. Once the case bolts are snugly tightened, try to turn the crankshaft and the transmission shafts. The transmission should turn easily, and the crankshaft should turn with some resistance. Using the plastic mallet, tap lightly on the transmission shafts while spinning them. Do the same with the crankshaft, tapping on both ends. The crankshaft may make a sharp cracking sound. That is good because it means that the crankshaft has centered between the main bearings. Now torque the bolts on the cases.
FINAL ASSEMBLY
Assemble the rest of the engine components, mount the engine in the frame, hook up all electrical wires, control cables, and linkages. Torque all the mounting bolts, and then you're ready to break in your rebuilt engine.
BREAKING IN A NEW BOTTOM END
The new lower end will need some patient break-in time. The best way is to let the engine idle for three separate 10-minute sessions with a 20-minute rest period between sessions. You don't need any extra pre-mix oil because the engine load is minimal when the engine is idling.
This is based on a dirt bike 2-Stroke but still is the same principle. I hope this helps you. Let me know if you have any other questions. Good luck with the sled! --Arcticatman
