Atco Villiers timing set up

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Weldspec
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Atco Villiers timing set up

Can anybody help me with setting up timing on Villiers mower. Has the notch on the crank end so when piston at tdc I need help where the magneto should be positioned . Appears the only mark on the magneto is a number one stamped on it . Not sure if this has any relevance to timing . Any help much appreciated 

wristpin
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In general terms you are

In general terms you are setting the point before TDC when the spark occurs expressed either as degrees of radial movement of the crank or the linear movement of the piston. As these vary from engine model to model we need to know what model Villiers you have. I'm assuming that your question arises because you have an  engine with a flywheel that is just on a taper and not located by a key.

First you set the contact breaker points gap to the correct figure (on a lot of two-stroke Villiers it is around 15 thousandths of an inch), then you lower the piston by the specified BTDC figure and move the magneto stator plate or flywheel so that the points just start to open. 

Exact details of your engine will enable a more precise answer applicable to that engine.

This may help

https://www.oldlawnmowerclub.co.uk/technical/villiers/magrebuildhome

Weldspec
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Morning 

Morning 

the only details I have is that it’s a 1956 2 stroke . On the engine itself it has stamped on it 4783 and also 428B. Don’t know if that helps sorry 

regards Alistair 

wristpin
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No arrow stamped into the rim

No arrow stamped into the rim of the flywheel?  If so, it will make things easier but if not it can be done from basics but we will need to find the dimension for the piston position before TDC applicable to your engine.

Weldspec
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No sorry no arrow stamping on

No sorry no arrow stamping on rim of flywheel . Where do I go from here . Trying to find information isn’t as easy as I thought . I really do appreciate your input . 

Alistair 

olcadmin
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Sometimes there is a small

Sometimes there is a small notch in the end of the crankshaft - when it's vertical the engine is TDC.

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Weldspec
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Yes got the notch on the

Yes got the notch on the crank but need to know where the flywheel should be positioned as I have no reference stamped on apart from a number 1 

wristpin
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OK. First, the reference to

OK. First, the reference to TDC being when the notch is vertical only applies when the engine cylinder is vertical ! Otherwise it is meaningless. In your case, with an angled engine just get the notch pointing more or less at the spark plug.

First off you need to know the amount of piston travel before Top Dead Centre that gives the correct firing point for your engine. I don’t have any reference material for that engine but hopefully another Club member has, but just for the purposes of this exercise - 5/32”.

Then thoroughly clean and adjust the contact breaker points. The recommendation for most Villiers two- strokes is 12-15 thousandths of an inch. This requires the flywheel in place ( relationship to the crank is irrelevant and it just has to be in place on the taper- not tightened up ) and turned to give the widest points opening . One of the “ windows” in the flywheel  will correspond to the peak of the cam allowing you to do this. When you have set the points to, say 14thou, remove the flywheel insert a bit of clean thin card or copy paper between the points and gently pull it through to remove any grease left from your feeler gauge. Don’t pull it right out or the points may grab it and leave fibres  between them , causing trouble later. Open the points manually to release the paper. Refit the flywheel firmly but not tight.

Find Top Dead Centre. Using the notch to give a rough indication insert a pencil or dowel through the spark plug hole to contact the piston. Then rotate the crank a few degrees in either direction to find the highest point  of travel . That is a bit of a “ black art” convincing yourself the location of the exact point! Even using a Dial Test Indicator gauge still requires a bit of judgment. There is a 100% accurate way of ascertaining TDC, the Positive Stop Method, but it's really only needed for high performance engines and cam timing.

Next you require a lump of plasticine  or Blue Tack and a wire paper clip. Squeeze the plasticine onto the fins, straighten the paper clip and embed it so that you have a pointer against the pencil and make a TDC mark. Remove the pencil and make a mark above it the required BTDC piston travel (5/32?). Reinsert the pencil and check that the pointer still lines up with the TDC mark. Then carefully rotate the flywheel in the opposite direction of engine rotation so that your BTDC mark lines up with your pointer. There (at last!) you have the firing point - that is the point where the contact breaker points just start to open.

So, releasing the flywheel just a smidge so that it does not turn the crank , rotate it a few degrees either way and watch the points to see when they start to move . The time honoured way is to place a bit of "fag paper" .between the points and put just a little tension on it so as to feel when the points relax their grip. Now hopefully with out disturbing the relationship between flywheel and crank tighten it good and firm using the Villiers hammer drive spanner or equivalent.

Then recheck that nothing has moved and you are done. It may sound horribly complicated so be prepared to have a couple of goes, then it will all start to make sense.

Because I do quite a lot of such jobs and also like gadgets I've made myself a TDC gauge using an old spark plug body with a sliding calibrated plunger which saves fiddling around with the plasticine and paper clip and I also have a 1960s electronic gadget the Rupert Ledger Dy-Tone that gives an audible signal of points opening, so no messing with fag paper. 

 

 

 

 

 

Weldspec
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Thanks again Wristpin 

Thanks again Wristpin 

something tells me tonight is going to be a long one 

regards Alistair 

Weldspec
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Just updating 

Just updating 

Thanks to everybody for the help and input on the villiers timing . Took my time the other night making everything right as far as I thought and she sparked into life .Over the last few days it’s started up straight away . Now that I have a runner I’m now on the hunt for info on the original set up for front rollers as mine has been modified with wheels . Also require the correct grass box .

regards Alistair 

wristpin
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Your "modification" may in

Your "modification" may in fact be an optional high cut set-up which was not an unusual accessory for cylinder mowers. It possibly means that the roller assembly resided on a shelf in a previous owners shed or garage and remained there when the mower was disposed of..

OLC member Clive Gravett may be a useful contact for the roller and grass box .

Anything like this?

https://www.dropbox.com/s/hw30pmdc6z0vsgs/Atco%2012%20inch%20two%20strok...

Edit. Just found the pic of your machine on an earlier thread. I would say that those wheels are definitely a home made improvised high cut mod. Probably all you need is a set of rollers to go onto the existing shaft