How is the air cleaner? Most have a wire mesh inside the canister that needs to be removed and cleaned periodically, often over looked. Try a test run with the tube disconnected, see if there is a difference.
Check for vacuum leaks. Spray some flammable type carb cleaner, or use an oil squirt can with some gas. Carefully spray around the gasket areas with the engine idling. Listen for changes in engine speed, sound. Another thing that occasionally shows up, an internally burned through siamese manifold. This is where the exhaust and intake manifolds are cast or bolted together in such a way they can burn through internally and cause exhaust to enter the intake. About the only way to do a for sure diagnosis is to remove the manifold and fill it with water, look for it to transfer from one to the other. (This only applies if your manifold is so designed.)
Have you set the valve clearance? If not, take a look at the entire valve train, look for broken valve springs, bent pushrods, etc. Remote possibility there is a loose valve seat, but let's not go there yet.
Is the thermostat in and working? A 180 or 195 thermostat will help keep the engine cleaner, make it run cleaner, last longer, get better economy.
How is the distributor? Is the shaft bushing/bearing tight? Any side play will let the point gap change at random, do strange things.
If there is any doubt about the points, replace them. Also try a different (preferably an old) condenser. Points and condensers have a terrible reputation now, the quality is just not there. All ignition components are aftermarket. Look closely at everything, compare it with the original, assume nothing!
Is the centrifugal advance free and the springs in place? The timing can be generally set by ear. As long as it isn't kicking back against the starter, clattering under load, backfiring, or loss of power, it is probably close enough, just play with it a bit, you'll know when it's right.
When it was converted to 12v, what was done with the coil? Getting the correct coil or coil/resistor combo is critical. Get it wrong, it will have a weak spark, or overheat the coil and points. It can have either a true 12v coil, or a 6v coil and a resistor.
The best way to know is to check the resistance across the primary coil terminals out of circuit. A 12v coil will have about 3 ohms resistance.
A 6v coil will have about 1 1/2 ohms. A 6v (1 1/2) + a ballast resistor (1 1/2) = 3 ohms. Check the resistance across the - primary terminal to the ign side of the resistor.
Best to test the coil, not rely on what was bought or what the can says. A proper coil will make at least a 3/4" spark at the coil tower, and will run at about the same temperature as the surrounding engine components.
The fuel system:
If the tank is flaking rust or the liner is coming loose, something will have to be done eventually. If a new aftermarket is unavailable, there are universal tanks on Ebay, other solutions.
An easy test for fuel delivery, and this (as is any other test) is best done when it is acting up, with the engine off and the fuel valve open, pull the drain plug in the carb bowl. Be ready to catch the flow in a clean glass. It should have a full flow, not slow to a drip or stop flowing.
Look at what is caught, if it's dirty there is still contamination in the tank. If there is a loose liner, it will continue to produce trash.
If the flow is insufficient, could be a clogged screen inside the tank, in the sediment bowl, or the screen in the carb inlet fitting (if equipped). If there is an inline filter, that can be a problem. They don't work well with gravity systems. If there is a fuel pump, check it's performance.
Jetting the carb:
Adjusting the carb is the last thing on the list to do. Everything else MUST be right, or it's an exercise in futility. Be sure the float level is to spec, the engine oil is clean and not contaminated with gas.
Start with the engine warmed up, air cleaner connected and serviced, clean gas, as said, everything adjusted and in spec.
Adjust the idle mixture first. The engine must be idled down to the 400-500 RPM range. Any faster and it will be off the idle circuit.
Turning the idle mix screw in richens the mix, out leans it. The screw adjusts air bleed, not fuel flow. Turn it out until the engine falters, back in to best idle. The adjustment is minimal, but it should make a difference. If it doesn't, the circuit is clogged or the idle speed it too high.
That the main is not adjustable, not much can be done short of changing the jet or converting it to an adjustable jet. To test the mixture, with the engine at slow idle, fully and suddenly open the throttle. The engine should respond crisply, without hesitation. A single puff of black smoke is desirable. But only a puff, it should not continue to smoke once up to speed. This only applies to black smoke. Blue smoke is oil, another story.
If it continues to black smoke, the area around the tail pipe is black soot, then it may need a smaller jet.
A lot to digest, but do one thing at a time. That way what was done can be undone if it didn't work out. Let us know how it goes...
Upload one or more videos to your post. Photo and video filesizes should be less than 5MB. Formats allowed are gif, jpg, png, ogg, mp4, mov, and avi. Be sure to use filenames without spaces or special characters, and filetypes of 3 digits lower case.
We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]
Today's Featured Article - Talk of the Town: How to Remove a Broken Bolt - by Staff. Another neat discussion from the Tractor Talk Discussion Forum. The discussion started out with the following post: "I have an aluminum steering gear housing with a bolt broken off in it. The bolt is about a 3/8" x 1 1/2" bolt. I've already drilled the center of the bolt out with about 7/64" drill bit the entire length of the bolt. Only one end of the bolt is visible. I tried to use an easy out but it wasn't budging and I didn't want t
... [Read Article]
Latest Ad:
2022 John Deere 5045E, 4wd, front end loader and 3rd function with grapple. 120 hrs, 55k new, must sell
[More Ads]
All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy
TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.
