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Alan's Fairy rebuild

Started by GlennMckenzie, 05 Jul 2018 at 13:20

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Hi Forum members.
I thought I would share this rebuild with interested forum members as we will need some technical advice along the way.
Alan has been kind enough to assist me multiple times over the years with bits and pieces so I recently offered to repay the favor by helping with the rebuild of his 1907 Fairy Engine.
Stay tuned, I may have questions


I CNC machined a new 36 Tooth Camshaft gear, I modified the tooth shape slightly to better match the well worn Crankshaft gear.


The Cam Shaft and Gear cant be one piece unfortunately. Because of the casting overhang inside the crank case the gear has to be fitted after the Camshaft has been inserted.
An internal nut or screw holding the gear onto the Camshaft would destroy the engine if it came loose, so I decided to cut a square spigot on the Gear with a corresponding square pocket in the Cam. The idea is to run a bolt from the outside all the way through to the Cam gear. This bolt would later attached the distributor arm/rotor to the Camshaft (outside the engine). My thinking is, if the bolt ever comes loose the engine will stop because the rotor will stop turning. 


This is where I need some expert advice.
Machining the Cam shape onto the new Camshaft Shaft. 
In relation to the teeth on the Cam Gear, where should the highest point of lift be?
36 teeth will give 10 degree increments of Cam adjustment already, Is this close enough for Cam timing?
Thanks Glenn


Thoughts please?

Looking at the first photo I posted of Alan's Crankcase.
Im wondering how the ignition Timing/distributor housing is mounted to the front of the Crankcase.
One Idea would be to replace the existing Camshaft Bronze bush with a longer one, the Distributor housing could then rotate on the extended bush to advance and retard the timing.
This photo shows the rough remains of a distributor housing on what looks to me like an extended Camshaft bush?

Thanks Glenn



           You asked for our thoughts - I may be wide of the mark, but here goes!
  Firstly, you say the cam and gear have to be separate to insert them into the crankcase - I don't think this is the case. As this engine has automatic inlet valves and is a flat twin, then the camshaft will have just a single lobe that operates both exhaust valves. If this is the case, then the cam and gear can be rotated to a position where it will go into place and then turned to the correct timing position, and then the crankshaft inserted into the crankcase to mesh with the cam to give the correct timing.
   You also mention a distributor. Bearing in mind the age of this engine, it probably had trembler coil ignition - in which case a cam or flat on the end of the camshaft probably operated a make and break for the trembler coil.



Thanks Eddie,
The Cam slides in past the Crankcase easily as you mentioned. Its the 36 tooth Gear that wont fit.
Interesting video on this site showing the Fairy's trembler ignition in action. I will leave that part for Alan, I'm just machining the missing Engine parts.
I digitized whats left of the original Cam and machined the Profile onto the new Camshaft today.


Having the cam drive gear inside the crankcase is reasonably common on early bikes: here's the setup on my 1903 Bradbury. Note the wiper for trembler coil.

I'm not sure about the original Fairy ignition but 1907-08 is very late for trembler coil, which was poorly behaved at higher revs. An ordinary HT coil would perform better and (other than some notable exceptions like the T Ford!) took over from trembler after after the early 1900s.

Regardless of trembler/induction coil, I assume the Fairy doesn't have a distributor, but instead has a wasted spark.





Hi Ian,

It does look like the Bronze Camshaft Bearing extends out past the Crankcase. So the timing rotor thingy (I still recon its a distributor) slides over the extended bush.

Perfect thanks.


There is a wipe contact arrangement on the end of the crank, and that has the advance retard. No wasted spark - there is a rocking distributor that fits on the spot at 2 o'clock, and a plunger is pushed by a second cam on the cam wheel. I'd have to pull the engine apart on mine to show what it looks like.
This distributor is what we need the details of from the chap in NZ Glenn


A bit of progress in the last few weeks.

Re-machined the pushrod holes as they were welded over.
Made new pushrod guides.
Machined new cam followers/pushrods from 1/4" Ejector pins and had them heat treated.
CNC milled the small Aluminium cover at the end of the Crankshaft and the new Distributor Housing thing.
1/4" bolt now locks everything together from the rotor back through to the Cam Gear.

Still quite a bit to do cosmetically and mechanically. The engine is missing a lot of fins on rear and I need to look at the inlet valve area as I don't think the Brass bits hanging out the end of the cylinders are original. From what Iv seen in other photos there should be cast Iron plugs screwed in the ends holding the atmospheric inlet valve assemblies in position. As shown in the photo below.
Also, still undecided what to do with ignition. I was thinking of hiding some points inside the Distributor Housing body and running wiring back up to a hidden Battery and coil. Not my preferred option as this would give spark to both Cylinders simultaneously. The other option would be hide some fancy new electronic ignition system somewhere.

Ideas anyone?



We've discussed the Fairy inlet valves in an earlier thread:

On the Fairy, the atmospheric inlet valves live in horizontal cages that are held in place by the hex-head plugs, and the manifold attaches from underneath.

The Fairy distributor is whacky, but interesting!




Hi Forum members,

Its been a while since my last update.
Engine is mechanically finished and I have managed to fit some points I found at Laidley Swap inside the now slightly larger distributor housing. Made an exhaust and replaced all the broken fins. Engine spins over freely and is showing signs of life.

I made a couple of dummy engine mounts out of some fence clamps and roughly fitted the Engine for the first time Today.
The Engine is sitting a bit high at the moment, some shorter mounts will fix that problem.



Just out of curiosity Glenn, what's the other bikes in the background?


That's what I was thinking about too. I'm guessing a Triumph P model and perhaps and AJS? It's nice to see them in original patina.


Model N Triumph and 1925 AJS


A little more progress this week.

I machined up a bearing housing block that clamps onto the lower Frame for the idler gear and drive pulley.
Everything is roughly aligned at this stage, waiting for the rear wheel for final alignment.
Left crank pedal arm is hitting the Pulley so I mite have to make a short extension? I don't think a more aggressive bend will do it.

Cheers, Glenn


More progress


Hello forum members,
I have pretty much completed all that I can do on Alan's 1907 Fairy project. I'm pretty happy with the results considering what we started with.
I'm handing it back to Alan at the upcoming Maleny Swapmeet in a couple of weeks and Alan is bringing a suitable Seat and Handlebars so I will add a couple more photos from the day. With the addition of a small battery and a couple of coils hidden inside tank the engine should now run. We ended putting an updraft TS Carby on it until something more suitable can be found, although it doesn't look too out of place.
Apparently Alan has lined I a local guy to fabricate a proper replica Tank for the bike in the future.
Thanks to everyone that assisted with the project along the way.
Cheers, Glenn