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Old 11-08-2015, 08:51 PM   #1
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Post Lucas K2F Rebuild Tech, As Requested.

.As requested, here is some rebuild tech on the Lucas K2F and K2FC magnetos. Bear in mind that I use a third party vendor to re-magnetize the case magnets, and when necessary, to replace armatures as a last case scenario. If those two items of your magneto are in good shape, the tips below can get your Lucas mag on the road, AND reliable. If you NEED re-magnetizing, or a new armature, This tech will at least have the rest of the mag in order and looking good before you ship it off (read: lees work for rebuilder = less overall cost) Please be patient, as I am working on this between several client builds and a backlog of parts orders.

I will also offer one of the MANY ways to time your mag. The way I will show requires only a timing light, degree wheel, and a drill, and is by far the fastest way that I have found to get your mag timing SPOT ON.

I forgot to take a pic of the actual mag I am servicing, but it was a bit worse than the one below...

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Old 11-08-2015, 09:00 PM   #2
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Default Re: Lucas K2F Rebuild Tech, As Requested.

Full dis-assembly is the first step. Be sure to remove all brushes and screws from the body of the magneto before attempting to pull the armature out (The slip ring will be damaged if you skip this step). The condition of the mag shown will reveal why I don't recommend even trying to run an old, unknown-condition magneto.

Issue one: points cam ring. This is as bad as I've seen. "When you come to the last page, close the book"


New one going in...


Well, at least whoever did this understood the concept. This bit of rubber was placed here as insulation.


This red insulator was missing, but now it is back...

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Old 11-08-2015, 09:07 PM   #3
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Default Re: Lucas K2F Rebuild Tech, As Requested.

The points plate should have a key protruding from this boss, not sitting flush. Someone tightened down the points plate before indexing the points plate to the corresponding slot in the armature.


All is not lost (sometimes). This key can be carefully restored to it's correct position with some patience and some careful application of force. This brass alloy is fairly forgiving. If you position the key at 6 o'clock, place a small flat screw driver directly on the depressed key, and tap it gently, you can get the key right back where it needs to be.


If you go too far or too fast you will ruin the points plate. Take your time and test fit it to the armature with each tap. Before you know, it will be perfect.
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Old 11-08-2015, 09:30 PM   #4
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Default Re: Lucas K2F Rebuild Tech, As Requested.

Once the mag is apart, I remove the bearings and races, put the alloy cases through the parts washer, glass bead blast them, then clean them with brake cleaner and compressed air.
The races were too crusty to go into a fresh mag, so I pulled some old good ones out of the magneto parts stash.


After cleaning, it is time for new seal, races, and race insulators. I made this tool for installing the seal/insulator/race in the mag. The background shows the points housing with new race and insulator installed.


Smear just a bit of Three bond onto the seal, line everything up on the tool...


Give it a firm push, and the case is ready for the armature.
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Old 10-22-2016, 10:58 AM   #5
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Default Re: Lucas K2F Rebuild Tech, As Requested.

Sorry about taking so long to update this thread. It's been busy here.

The armature was up next. Assuming the edges of the slip ring aren’t destroyed (spool looking bit on the right) I skim the earthing path (on left) and the slip ring valley on the lath to keep the brushes from bobbing around in their holders. Skim off as little material as possible.


Pop the bearings off the armature and clean them with solvent and a brush to remove any petrified grease and grit, blow them dry and pop them back on the armature. Grease them right before final assembly.


The condensor: Don’t plan on it working. Even a new-old-stock magneto will need its condenser replaced. This part of the service is revolutionary, compared to the old way of condenser replacement.

On the drive side on the armature, 180 degrees from where the slip ring tower goes into the armature, you’ll see two wires that are soldered to the stock condenser. Unsolder the two wires from the metal terminal, twist them together and re-solder them. Insulate them with heat shrink, and tuck then back in so they won’t move when the armature spins. This operation removes the tired condenser from the circuit. This picture shows the two wires, freed from the condenser, and soldered together…


The new condenser setup will not require taking the magento apart to this level again. It will only require taking the stationary points boss off the point plate.

Take a moment to remove the points arm and boss from the plate and file both contact faces of the points. They do not have to be filed perfectly flat; just make sure they are clean. This type of condenser can be bought on ebay from user “skipsoldbikes”. They cost about $30, shipped. This picture shows the Bright-Spark condenser installed in place of the thin plastic insulator under the points boss. We have run this new style condenser on our personal bikes and on client bikes for years with ZERO failures. It is WELL worth the modest cost.


More history with this magneto body, in the form of stripped threads. One Helicoil later and we are back in business.
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Old 10-22-2016, 11:04 AM   #6
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Default Re: Lucas K2F Rebuild Tech, As Requested.

When you install the armature into the magneto case, and bolt down the points housing, you should have about only a couple thousandths of end play. When you turn the armature by hand, if it feels like it is binding at all, STOP, determine why and sort it before proceeding. You may need more points housing shim, or the slip ring safety screws could be too long (wrong ones).

To install the pints plate, make sure the key is properly registered in the armature’s slot. Install the ¼” bolt. Remember to re-torque this bolt after the first few miles to be sure it is fully seated. Gap the points at .012”. The gap should be the same on both lobes of the cam ring.


This magneto was formerly manual advance. We are going with auto advance to keep the handle bars free of clutter. But this leaves a hole where the manual advance used to live. This “rain collector” was likely the likely culprit for the very rusty cam ring.


To keep water out and have a nice finished look, I turned up an alloy bung that is threaded 26tpi for the housing and tapped ¼-20 for the stainless socket head bolt.


On your pick up and earthing brushes, clean them well with brake cleaner, and verify they are dry and move freely.

When you get the magneto put back together, clamp the bottom mounting tab in a vise to test it. Use spring clamps to hold the spark plugs on the upper mounting tabs. I use a short bit of fuel line and a drill to spin it counterclockwise. Your fresh mag should be able to consistently create a spark across a .200” gap at 200 RPM. The spark should be thick, bright, and dead consistent.



Looking good and working like a champ!


There are also a few tests you can conduct on the armature, while it is out, with a multi-meter to let you know the condition of the windings. These tests, a list of Bright-Spark vendors, and magneto service centers can be found at: www.brightsparkmagnetos.com However, you have nothing to lose besides some of your time and a few affordable parts to service the magneto as shown. If your armature and magnets are in good shape, which is not unheard of, you will have a reliable Lucas magneto again, and you will have the pride in knowing you did it yourself.
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Old 10-23-2016, 08:26 PM   #7
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Default Re: Lucas K2F Rebuild Tech, As Requested.

Quote:
Originally Posted by MP4/8 View Post
Thanks for taking the time to do this. It will greatly help me. I have two questions, first, I have a lucas k2fc. Whats the difference between the k2f and k2fc ? You mentioned manual advance and converting to auto advance. Whats involved with that and advantages ? I am familiar with mags on cars, and the effects of no advance. Is it the same thing ?
Thanks for any help. I have just started on building my first preunit triumph.
Here is the difference between the K2F and the K2FC. Different pick ups. Competition on left, standard on right


The auto advance timing gear is on the left. The alloy gear on the right is a reproduction of was used for fixed timing and manual advance. On solid gear setups, timing advance was done manually by a lever on the bars. While I have run fixed advance before, but using an AA gear yields a nice low tick over, easy start, and good performance.

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