These instructions came from Lionel Roach, aka JONAH so no photos are available.  Since this is not my article I accept no liability or responsibility for its content.  However, I have used these procedures with success on all of my Marlin rifles.  My notes are in red.
    
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Those involved in Cowboy Action Shooting (CAS) have never had it so good when it comes to firearms and related equipment. While some manufacturers were slow to climb aboard the bandwagon, others listened to what shooters wanted and responded. Marlin Firearms worked with shooters and gave us the Model 1894 in it's many guises.  An informal count of the number of Marlin Model 1894's at any CAS shoot will show how popular the Marlin has become. At our club, Tin Star Texans, at least fifty to sixty percent of the rifles being used will be Marlins.

A sideline industry has emerged to tune and modify the firearms used in CAS, but individual owners can perform many of the tune up procedures. There are some parts that are best left to the professionals or at least advanced amateurs such as sears and hammer notches. However, with a little bit of time and minor tools, the average owner can do a good job of smoothing up the action.

TOOLS AND EQUIPMENT
Before you attempt to do any work on your rifle, get a good set of gunsmith screwdrivers. Do not try to use your hardware store special screwdrivers. Burred screw heads will result from use of standard screwdrivers. Gunsmith screwdrivers are available from Lyman, Chapman and others. If not available locally, gunsmith screwdrivers can be ordered from Midway, Brownell's and others.

Additional equipment required will consist of a sheet each of 400 and 600 grit wet or dry paper. Nice to have would be a few small hones, but the wet or dry paper will get you by. When we begin to work on the hammer, a belt sander or bench grinder will be required for part of the procedure.

INSPECTION
Before beginning with the actual tune up, cycle the action slowly and try to determine where in the cycle roughness is felt. The areas to pay attention to are the lever plunger that holds the lever up, the carrier lifting up, the bolt sliding in the receiver and the bolt passing over the hammer. All of these areas will most likely require attention and will be addressed during the tune up.

Unless you have been shooting your rifle a great deal, I recommend that you cycle the lever several hundred times prior to beginning any work. This will accomplish two things. First, it may smooth out any burrs that are there. Second, it will leave burnish marks on the areas that are in contact so you can identify those areas needing work. Before disassembly, slowly open the action and observe the point at which the hammer comes to full cock. On my Marlin, the bolt depressed the hammer another 3/32" after reaching full cock. I have observed the same amount of over travel on other Marlins. We will address this when we work on the hammer.

DISASSEMBLY
Begin disassembly by opening the action about half way and remove the lever screw, the lever, the bolt and the ejector.

Remove the rear tang screw and slide the stock of the rear off the action.

Lower the hammer by depressing the trigger safety block. Hold the hammer under the thumb, depress the trigger and let the hammer go forward against the frame. Remove the hammer spring by sliding the hammer spring plate to the left side and then remove the hammer spring. Remove the hammer pivot screw and remove the hammer through the clearance slot by rotating it upward.

Turn the rifle over and remove the trigger guard plate support screw from the left side of the action. Then remove the trigger guard plate screw from the bottom. This is the screw just in front of the carrier leg slot. Note that this screw is longer than the previous screw. Lift up on the lower tang and remove the trigger guard plate. Remove the locking bolt from the bottom of the action.

Remove the carrier screw from the right side of the action. The carrier will now fall out of the bottom of the action. There is no need to remove the loading gate screw. The action is now dissembled as far as required for the tune up.

LEVER
Inspect the lever for any burrs on the end where it bears on the carrier and bolt. Burnish marks on the end will show where it is in contact with the carrier and bolt. Lay a 2" by 2" piece of 400 grit wet or dry paper on a flat surface near the edge of your workbench. Place one side of the lever flat on the paper and polish the side. Then flip it over and polish the other side. Polish off any burrs found on the two narrow edges. Stay clear of any of the areas that will be outside of the action so that you don't remove any bluing. This is a polish only operation. Do not remove metal or change the shape of the end of the lever.

The finger lever plunger will need to be polished and the spring tension reduced. With a small punch or nail with the end ground flat, remove the plunger pin. The plunger is under tension, so be careful and don't let the plunger and spring jump out and get lost. Hold a finger over the plunger end or put a small rag over it to contain it. Using the 400 and 600-grit paper, polish the two bevels on the end of the plunger. Check the shank of the plunger and remove any burrs you may find. Place the spring back on the plunger and insert it into the hole in the lever. While looking through the pin hole, push the plunger in until the hole is clear.

Continue pushing in the plunger until it is flush or nearly so. This will give you a good idea of the amount of the spring that can be removed. In my rifle, I removed two coils by cutting them off with a good pair of side cutters. I recommend that you only cut one coil at a time and then try the plunger in the lever for tension. The plunger must have enough tension to fully extend and lock the lever in the closed position.

TRIGGER GUARD ASSEMBLY
Unless you are experienced in working on sear surfaces, I recommend that you leave the trigger and sear alone.  (Refer to my article Working on the Marlin Lever-Action Rifle Sear)  Take the trigger plate in your hand and look down into it from the top side. You will see the trigger block safety spring. This spring also bears on the rear of the trigger. Using a small screwdriver under the short leg, the one bearing on top of the trigger safety block, pry up on the spring approximately 1/8". You want to bend this leg upward enough to relieve tension on the trigger safety block. Don't try to get all the bend in one try, but bend it up a little, try the trigger block safety for tension by pushing it up from the bottom behind the trigger. Continue bending and trying until you can easily move the safety block up with your finger. Leave enough tension so that the safety block always returns to it's down position.

Now look at the long leg of the spring where it bears on the rear of the trigger. Pry it up a little at a time to relieve some tension on the trigger. Be careful and don't kink the spring. You are only trying to relieve some of the tension. It is better to error on the safe side rather than having to buy a new spring.

LOCKING BOLT
Check for any burrs and polish the sides and any burnished areas. Do not remove any metal or change the shape.

BREECH BOLT
Place the bolt back in the action and slowly slide it back and forth. It should move smoothly throughout its length. Check for any burrs on the bolt and in the receiver and polish them out if you find any. Carefully polish the cam on the bottom of the bolt where it rides over the hammer nose. Do not reduce the height of the cam. Polish it only.  (I narrowed the width of this cam to about 1/16" using a flat jeweler's file.  This helped to lighten the action.)

HAMMER, HAMMER SPRING
Remove 3/4 of a coil from each end of the hammer spring. If you use a grinder to do this, do not let the spring become too hot to hold. Go slowly and grind the cut off end flat like it was done at the factory. If you do not have a grinder, use a triangular file to file a groove in the coil and break the end off. Then file it flat. A Dremel tool with a cutoff blade will also work to remove the 3/4 coil. In all three cases, do not nick the adjacent coil as this will set up a weak spot for future breakage.  (No matter what I did I couldn't get this modified spring to work in my Marlin.  I purchased an after-market spring from Brownells, which has worked perfectly.)

Using the wet or dry paper, polish the hammer strut on both sides and both edges. Check and remove any burrs from the hammer pivot hole. Polish the hammer screw where the hammer pivots.

Remember the 3/32" hammer over travel referred to above? Some of this can be removed by grinding the nose of the hammer down using a belt sander or fine grinding wheel. If you feel uneasy about removing metal from the hammer, skip this step. You need to remove approximately 1/32" (.031"). Filing the hammer nose is not practical due to radius and the requirement to maintain the exact contour. Carefully grind and polish the hammer nose. I do not recommend removing more than 1/32" (.031"). This will assure that the hammer is sufficiently depressed to be held at full cock. Scribe lines on both sides of the hammer nose following the same contour and remove metal to this line. A better method of assuring that you don't remove too much is to use a vernier caliper and measure from the flat on the bottom of the hammer to the nose. Go slowly, measure often and then polish the nose. Be advised that altering the hammer may void the manufacturer's warranty.

CARRIER ASSEMBLY
Leave the sides alone. Polish the burnished areas where the lever acts on the carrier. Check the screw hole for burrs and remove. Polish the screw where the carrier pivots.

EJECTOR
Check for burrs and polish as required. Polish the cam area where the bolt pushes the ejector down into its slot in the receiver.

MAGAZINE PLUG
Remove the magazine tube plug and remove the 10 shot plastic plug from the spring. Replace the magazine tube plug and you can now load 13 rounds in the magazine. I don't recommend that you remove any coils from the magazine spring unless it is hard to load rounds into the magazine. If you do decide to remove any coils, proceed slowly and try often for proper feeding. Be safe, leave this spring alone.  (There needs to be enough spring tension to push the last round from the magazine tube onto the carrier.  Test this by loading only one or two rounds into the magazine tube.)

SAFETY
Everyone complains about the safety. However, it does have a couple of good traits. One, it allows you to safely cycle rounds through the action to unload the magazine without the danger of an accidental discharge. Two, you can dry fire occasionally without danger of breaking a firing pin. [Five] things can be done to the safety. 

1. Leave it alone and use it when desired. 
2. Replace it with an after market dummy safety that fills the hole and appears as a bolt. 
3. Turn in the safety set screw enough to freeze the safety in the off position so that it won't get applied accidentally. 
4. Face off the left end of the safety so that it is flush with the left side of the receiver when it is in the off position. The safety can still be applied if desired by pushing it on with the end of a pencil.
5. Put a rubber 'O' ring over the safety.  This will prevent it from being engaged accidentally, but with a little extra finger pressure, it can still be engaged.  This method does not require any modification to the rifle.

REASSEMBLY
Reassemble the rifle in the reverse steps to disassembly. Put a light coat of oil on all parts prior to reassembly. Do not tighten any screw all the way until everything is back together. Then snug up all screws. Cycle the action several times to assure everything is working smoothly. On my Marlin, if the trigger guard plate support screw is too tight, the action will appear sluggish. If this occurs on your rifle, back the screw off very slightly.

LOOSE SCREWS
Every Marlin I have observed suffers from screws loosening up during heavy shooting. The most common is the carrier screw, but the hammer screw and the trigger guard plate support screw also may loosen. Keep a screwdriver close by when shooting and retighten the screws as required. A better solution is to apply a SMALL drop of blue Loctite to the threads of these screws. Loctite can be easily applied to the threads on the left side of the receiver using a toothpick. DO NOT USE RED Loctite or you may never take it apart again.

You have now tuned up your Marlin and are ready to enjoy the great rifle that it is.

Magazine Tube
Because I shoot light, target loads the brass cartridge case doesn't expand to seal the chamber so I get a lot of soot.  This soot gets into the magazine tube and will jam the follower, and will also absorb moisture and cause rust.  Part of my cleaning routine after a match is to clean and oil the magazine tube and spring.