Britbike forum Forums British motorcycles in general British motorcycles in general Francis Barnett Villiers Engine Question

Since Britbike is on a roll with the Francis Barnett questions, I figured I would add to the list. I am working on a 1926 Model 4 with the Villiers Mark VIIIc engine (147cc). My question is about the ignition timing, all the information I can find indicates to line up the mark on the crankshaft with the arrows on the flywheel. If I do this, the points open at about top dead center. This seems odd since most of the other two strokes I have tend to have the points open around 3/16" before top dead center or thereabouts. Does anyone have a measurement of the piston position where the points open for the VIIIc engine?

Thanks!

The Book of the Villiers Engine by Cyril Grange has a short chapter on the flywheel magneto,
and aligning those timing marks. 6th Ed 1939.

It covers a range of engines, and reference is made in places to the ignition lever -
does yours have such a thing ?

I thought that Villiers 2 strokes had fixed timing, I might need to read those sections in more detail to see what gives here.

The Mark VIIIC engine as shown,

That's the engine, mine does not have any adjustment lever for the timing, it is fixed. It has a small line on the end of the crankshaft where the flywheel is mounted, this line is supposed to line up with arrows stamped in the flywheel. Doing this puts the points opening at top dead center piston position. On my 1920 Clyno, the points are set to open at top dead center with the timing lever at fully retarded. When running, the lever is set at fully advanced, which probably sets the timing at 3/16" before top dead center. My Cleveland two stroke has fixed timing of 5/16" before top dead center. I sort of think the Francis Barnett should be somewhat similar.

Maybe you have a mix of parts ?
We might wait until Villiers comments here, my knowledge of prewar Villiers is a bit thin.

They were still learning about engines back then though.
In 4 strokes it was still decades away before they started making inlet valves larger than exhausts.
And in 2 strokes, before pulse timing and expansion chambers ruled the roost....

You do talk twaddle Rohan. Look at that Mk VIIIC. It has a primitive expansion chamber some six times the capacity of the engine and a short tail pipe some 60-65% of the header pipe. This is exactly the formula espoused by Yamaha in the late 50’s, early 60’s in their factory speed tuning manual.
Villiers knew far more about how to make a two-stroke go than anyone gives them credit for. After all, in the late 20’s Villiers 175cc engines held every World Record for speed, distance and endurance in their class. Repeat, every one.
Like all two-strokes back then major problems revolved around the poor quality of lubricating oils of the day. They were particularly susceptible to sticking rings, fouling spark plugs and what they called “varnish”. They clagged up horribly. Spark plugs of the day weren’t much chop either. Entertain yourself researching the introduction of spark plug heat ranges.
All that aside let’s discuss cycarmarks problem.
Firstly, the Villiers flywheel magneto was factory made as a set and stamped accordingly. It should have the same lengthy unique identity number stamped on both the back plate and the removable flywheel. Given Villiers made a range of flywheel magnetoes over their lifetime it’s always possible you have a mismatched set. Mostly this is not a problem but occasionally the mismatch makes things just impossible.
Secondly, the official factory ignition setting for the VIIIC is 1/4” btdc. As that dates from the 1920’s with something like 70 octane petrol it is just a starting point.
Thirdly, buy yourself a decent manual. The best general manual for your engine is “The Villiers Engine” by BE Browning and published by Pearson’s. First published 1949 the earlier editions will be of more use to you. Plenty of copies on Abebooks.com.
Browning covers all your questions. Forget the Cyril Grange books. Too superficial.
Look forward to hearing from you once you have digested Browning.

Thanks Villiers, I'll start with the 1/4" and work from there. Also thanks for the tip on the Browning manual, it will be very useful for this bike and the '39 Cruiser I have coming in a few weeks.

My little Villiers has a claimed output of 3 hp. Thats 24 bhp/litre.
The last time I looked, a recent KTM was getting 440 bhp/litre.
Now thats a commuter roadbike v's a full race bike with 60 years between them, but thats quite a difference !!!

I must find my Bowning, I've not needed to compare them to note there is such a difference.
Why is Grange mentioning ignition levers then though ?
Do most elderly 2 strokes not run fixed timing ??

I've got 6 two stroke bikes, the only one that has variable ignition timing is the 1920 Clyno (with CAV magneto). The Royal Enfield Cycar, Francis Barnett Model 4, BSA Bantam, Greeves 20DC have fixed ignition timing and are all flywheel magnetos and the Cleveland has fixed timing and a BTH magneto.

Does the Cleveland run any the better for it ?

There's a little bit more to expansion chamber design than just the volume and the outlet.

Eric Walsh and Clem Daniel made Bantams fo like the clappers with megaphone exhausts. Adding the rest of an expansion chamber makes them go better again.

The Cleveland runs very nicely with the fixed ignition. Here's a video of the first time I got it started:

Here is a video of the finished bike running:

Early Villiers magneto back plates were clamped to the timing side main bearing bush. With the clamp not quite tight and a suitable lever attached to the back plate for rider convenience it was possible to move the back plate and thus adjust the timing whilst on the go. Users found some sort of additional device, a ratchet, a clamp or even a rubber band was needed to keep the lever still once adjusted. It kept moving with vibration. I’ve never found it particularly practical for use while riding but good for getting the timing just so and then fully tightening the clamp. I make my own longer clamp screw so it protrudes out to where it’s convenient to reach. It’s then very easy to do minor adjustments.

The MkVIIIC is a much more pleasant engine if fitted with the later alloy Mk24C piston. It is identical except for being alloy and 1/3rd the weight. Makes for a much more lively engine and greatly reduced vibration.
Cheers,

The magneto back plate on mine is held with two screws so is non adjustable. My engine also has the cast iron piston, which as you say is pretty heavy. It is a nice running little engine but not as lively as the 150cc engine on my 1935 Royal Enfield Cycar with the aluminum deflector piston.

Usually Villiers flywheels are not keyed to the crankshaft. To set the timing the flywheel is pulled off the taper (most are self extracting), the crank is set to the correct firing position, the flywheel rotated until the points just open and then the flywheel pushed onto the taper and given a tap in the centre before tightening the nut

My flywheel is not tapered as you mentioned, and giving it a tap before tightening really helps hold it in place as it has to be nice and tight or it will slip into a retarded position.

Now I'm curious. So you are saying the fluwheel magneto on your Mk VIIIC does not attach via a tapered crankshaft? Essentially the Mk VIIIC stopped being used in motorcycles in the early 1930's when the improved long stroke 148cc MK 12C engine was introduced but continued on in multiple variations as an industrial engine for another 20 odd years. You are describing something like one of the myriad industrial variations not the motorcycle version.

What engine number is stamped on the crankcase? Not that even that is proof positive of anything as you may have a mix'n'match of industrial crankshaft within the original crankcases.

The motorcycle Mk VIIIC used the same crankshaft halves on both side of the engine. They are identical and always were for motorcycle engines. I have the relevant Villiers factory Spare Parts List sitting in front of me.

I look forward to the next installment.

I just re-read my post, my flywheel IS tapered, sorry for the confusion.

One interesting feature my engine has is the timing side crankcase has the long crankshaft bearing cut short on the outside of the case (cut pretty crudely) and a rubber seal fitted to the magneto back plate.

The plot thickens!
If there is a rubber seal in the back plate it should be fairly obvious to tell whether it has been modified to take the seal or it was built to take the seal when new.
If an original fîtting then you have a later model magneto from post war years. It may even be from a postwar industrial engine.
This is no great disaster as the later industrial engines used essentially the same set up but it could explain the timing mark puzzle.
As it happens BE Browning wrote two books on Villiers engine. The second one is titled “The Villiers Industrial Engine”. Also published by Pearson’s and also readily available on www.abebooks.com. Beware the number of firms doing “print-on-demand” copies at ridiculous prices.

This is fun isn’t it.

That's a very good point. The bearing was crudely cut, but the backing plate looks like it was designed to be fitted with a seal. The backing plate also does not have any provision for lighting coils, which may or may not confirm it is an industrial engine, but it sort of points that way.

This is an amazing amount of drama for 147cc's!

Thanks for your insight, it is much appreciated.

Yes, you describe all the hall marks of an industrial engine magneto. Alright if you don’t want lights I suppose. I have read that Villiers would supply early motorcycle engines without lighting coils for the truly desperate but I’ve never seen any. Every Mk VIIIC I’ve played with had lighting coils.
The rubber seal is the clue.
I’m most concerned about the cut back main bearing. I’m not keen on cutting down a main bearing where it has a large overhanging flywheel. Given the choice I’d give the seal the flick and revert to a full length main bearing but that decision is entirely yours.
It looks like “The Villiers Industrial Engine” will earn its keep on your shelves.

Cheers

In some of the Francis Barnett literature I have, it indicates "Electric lighting must be ordered with the machine, as otherwise an alteration to the flywheel magneto is necessary". I suspect the alteration is fitting a new back plate with the lighting coils.

That is a very good point about the bearing, something I will have to consider.

I've got one of the books on order!

It was an oddity of English motorcycling in the 1920’s that electric lighting was easily available on either expensive bikes or the very cheapest whereas acetylene lighting held sway in the middle. It seems to have taken a year or two for the buying public to accept the idea of permanent electric lighting on a cheap two-stroke. Given how expensive electric lighting usually was I expect most buyers would be a little wary at first. Plus of course if you still had the acetylene set from your previous bike why pay for something you already owned.

I’ve just had another quick look at the second , industrial engine, Browning book and it devotes a whole chapter to he Mk25C, the final iteration of your engine. It won’t add a great deal to your knowledge but knowing more about what you own can’t hurt.

The BSA Bantam and Royal Enfield Cycar I have both have flywheel magneto/lighting sets. They both work, but the lights are only bright when the engine is running at speed, when stopped, they are just barely adequate. I decided to just put a 6 volt battery in the toolbox on the Francis Barnett and use LED bulbs front and rear, it is plenty bright and I probably will not have to charge the battery too often. I went the same way on my '29 Douglas, after trying everything to get more output out of the BTH pancake dynamo. I have a Lucas acetylene lighting set on my '20 Clyno, but put LED bulbs in the lamps and a battery in the acetylene generator and ran the wiring through the rubber tubing. The thought of dealing with explosive acetylene gas was not appealing to me.

I'm looking forward to getting the book, one can never have enough information and I enjoy learning about the progression of the engine technology of the time. Another plus was when I was looking for the Browning book, I came across a Francis Barnett book by Goddard that seems to have some information about the J45 Cruiser I have on the way (it is somewhere in the Atlantic right now). Lucky for me it is the petroil model and not the pressurized Villiers lubrication system that was found on some of the cruiser models, although I enjoyed discussion of the system on another Britbike thread.

A Cruiser swept through my life and disappeared quite quickly. Nothing wrong with it except the owner, a good mate, was 1” over 6ft and couldn’t fit on it. Fine for me at an ordinary 5’9” but he was battering his knees to death on the leg shields. Not a happy owner.

I think that is why so many Cruisers “lose” their leg shields but my mate wouldn’t do that as they are an integral part of the design.

As to lights on two strokes I don’t like “direct” lighting either so usually go the alternative Villiers rectified lighting route. Works well with LED’s.

That explains why I found so many cruisers without the leg shields. The torpedo design seems to show better without the leg shields, but as your friend says they are an integral part of the design. The one I am getting has them and I'm 5'-10" so I should fit on it. I just barely fit on the Model 4, the handlebars are a bit cramped when turning, but otherwise I am very comfortable on the smaller bikes, plus I like the weight of them, easier to move around in the garage if needed.

My Greeves 20DC has the direct lighting headlight and the battery rectified tail light/stop light. It works well.