From Port Lines Hobbies

Replacing a smoke wick in a Flyer smoke unit is really quite simple........much simpler than these lengthy instructions would indicate at first glance!


The primary problem with smoke units that work fine when first filled, but quickly quit, is that the wick is hardened. The wick material is passing fluid along its length too slowly, so if it has been sitting, then there is fluid near the heating element, but it quickly uses it up when you start running the engine. Because the wick is hardened, it cannot "wick" new fluid along itself fast enough, and it soon quits. In SOME cases, a hardened wick can be freed up satisfactorily. Spray some "Tuner Cleaner" (I use Radio Shack's. It's expensive, but it's non-flammable ---unlike most others---, and it won't harm your plastic shells if it accidentally makes contact) down into the filler tube; 2 or 3 quick shots of it. Follow it with 6-8 drops of smoke fluid. Let it sit overnight, and try it out. You MAY see improvement. Of course, it if doesn't smoke at all, then the element is undoubtedly burned out. A replacement wick is called for, and it isn't an expensive repair.

Remove the smoke unit from the engine chassis by removing the 1 or 2 screws underneath the engine which hold the smoke unit in place. (BTW, I'm assuming this is a boiler unit.....not a smoke-in-tender unit. The basic replacement idea is the same; just a few differences in detail about access to it.) Unsolder the wires that enter the top of the smoke unit (make note of what went where).

Next , remove the six screws that hold on the cover plate and gasket. Also, remove the 4 screws that hold on the bottom plate and gasket. (Note that late-style smoke units had no bottom plate....just a single chamber, open from the top.)  [If you remove the bottom plate and gasket first, you will be able to determine if the wick is indeed hardened beyond hope, before removing the top plate and breaking the element in the process.]

Looking into the open top, you can easily see the burned wick. Just "rip" all that old wick out, through both the top and bottom. Use care not to damage the internal fiberboard insulating "box"; this is what prevents the wire winding on the wick from contacting the smoke box and shorting out. Clean out the inside well, making sure the two holes that connect the upper and lower chambers are wide-open and clean. You'll know why soon! Also, clean out and open up the holes in the solder-lugs on the cover plate, removing any leftover old nichrome wire wrapped around them.

Open your newly-purchased replacement smoke-wick. Note that the nichrome wire has been pre-wound around the wick, but has two long loose ends. If you have an ohmmeter, check the resistance across the two ends of the winding before you install it. It is likely that it has too many windings, which results in high resistance and low smoke output. I recall one that I checked had about 75 ohms resistance......almost double what it should be !  I had to remove about five windings from each end of the coil in order to get the resistance close to 40 ohms, an appropriate amount to produce a good volume of smoke even at slow speeds. Less windings results in more smoke output, but it also reduces the life of the wick slightly.  ( If you don't have an ohmmeter, I would suggest you consider buying one; you can get an inexpensive one at Radio Shack. It will also be very handy for you to have when determining whether armatures, fields, and other coils and solenoids are good, shorted, or burned-out. )

Now the frustrating part: you have to thread the two ends of the wick down through those two holes, into the lower chamber! First, use some sharp scissors, and clip 2-3 inches off one end of the wick, so that you have a nice clean-cut end on it. Apply a drop of smoke-fluid to the end, and twist it as tightly as possible. Form as clean and sharp a point as you can. Be sure the fiber insulator "box" is inserted into the smoke unit chamber, and that it's not blocking the air holes on its front and back side (in fact, make sure that rear air hole isn't plugged! Stick a pin through it!) . Then carefully feed the wick through the hole , using a twisting motion. As soon as you can do so, grab the end of it from below with a pair of tweezers, and pull it through (almost to the wire winding). Repeat this process on the other end of the wick. We offer a Smoke Wick Tool which will enable you to pull that wick down through the holes in seconds! Use it like a "lasso" to just barely grip the tip of the wick and pull it down through the hole (don't get too much wick through the loop or it will be too thick to pass through the hole).  (TIP: If you really get frustrated with "threading the needle", you can use a drill to enlarge the two holes in the smoke chamber a bit. There is no good reason they have to be as small as they are.....drill to enlarge them a little bit, and threading will be easier!)

An aside here---- If you are repairing the later-style smoke unit which has no bottom plate, the task is a bit easier. You feed the ends of the wick through the two holes in the black internal insulator "box", stuffing all the excess in the bottom of the unit. Remove some of the excess length on the wick, if necessary.

You should end up with most of the wick in the lower chamber, and only a small portion (containing the wire) centered in the upper portion (low enough so it won't rub against, and burn, the cover plate, once installed). Now feed the two loose ends of the wire up through the two solder-lug holes in the cover plate. Let them hang there loosely for now.

Add two or three drops of fluid right near the coil, so the wick will be ready to test in a few minutes. Now, one of the most important points! Inspect the coiled wire on the wick closely (use a magnifier if necessary). Windings should NOT overlap or touch each other! If they do, the coil will short out and you'll have to start over! If two wires appear too close together, or touch, use a pin, or the tip of a razor blade to separate them. When you are satisfied that all is OK, carefully lower that cover plate down into position, making sure that the two ends of the wire still protrude through the solder-lug holes. Now replace at least 2-3 of the cover screws to hold the cover in place.

Wrap each end of the wire around the end of the solder-lug several times.  Next, stick the appropriate engine and light bulb wires back into the lugs, and re-solder. Note that nichrome wire cannot be soldered. Thus it simply is "encased" in the solder that holds the electrical wires in place. Clip off excess nichrome wire so that it doesn't touch the outside wall of the smoke unit chamber, causing a short.

At this point, I usually test the unit. Connect your transformer jumper clips (assuming you use some!) across the two lugs, and blow into the plunger- cavity. Hopefully, you'll see smoke billowing out of the unit! If not...... something's wrong!

Replace any remaining cover-plate screws and tighten all. Stuff the remaining wick into the lower chamber (it should not be packed too solid, or it will not allow fluid to wick through it fast enough), and tightly screw the lower gasket and cover plate back on. Then reassemble the unit, with plunger, onto your engine chassis.

Once you've done a couple of these units, you'll realize that they are really not difficult. It just takes a little patience!

Replacement wicks are available.


These smaller smoke units are constructed very differently. 
To rebuild these units,
1.) Unsolder the lead on the front of the smoke unit chamber which connects to the edge of the chamber ("ground").
2.) File away, or "unpeen" the front edge of the chamber.
3.) Now the front disk will pull out of the chamber. You will note that this unit has what looks like a wirewound resistor attached to the front disk; this is the heater element.  Inside the chamber should be some wadded wick material which absorbs fluid and keeps it in contact with the heater element. However, I have encountered many of these units with no absorbent material at all, which explains poor smoke production.
4.) If the disk is undamaged, you can clear the solder from the two holes, and replace the heater element( which we supply with a fiber sleeve around it). Test insertion to be sure the wire lead at the rear end does not contact the back of the chamber. (If you can't avoid that lead touching the chamber body, then just be sure that lead is the one that gets soldered to the edge of the body in step 7 below.)
If the disk is damaged, then you will have to salvage one from another unit, or make a replacement from something like circuit-board material.
5.) Disk is reinserted, with some soft wick material loosely wrapped around it, if you have any available. Don't wrap it tightly, however, so it doesn't burn.
6.) Seal the edge with epoxy, or JB Weld.
7.) Bend the shorter lead (the one from the piston end of the smoke chamber) over, and solder it to the edge of the chamber, like the original [this = ground]. (Be sure you do this with the correct leadů.otherwise you can create a short.)

Related parts available for smoke unit repairs include

Smoke-in-tender parts also available .

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