I'm not really sure what "Spot on" means when timing my 16H or ES2 when you have a mark on a piece of rod through the head or down an angled plug hole(ES2), that isn't easy to see and moves as you move your head, or wherever the rod is on a domed piston. "About right" is where I get it, and with what would seem quite retarded timing figures, I'm happy with slightly advanced, especially with better petrol these days than was originally used. As my 16H has been converted to slack wire advance on the lever, I can retard it slightly while riding along to see if it goes better... It doesn't and seems to like it slightly advanced.

I also fine tunes with the points gap as Henk suggested. Making the gap bigger advances the timing and smaller retards it on these mags, and there is quite a lot of adjustment to get it "Spot on". I haven't noticed a problem having the gap bigger but too small isn't good.

Tapping the sprocket on the shaft should hold it while tightening, but on a bike using a degree disc I find setting the timing a degree more, or less on the disc, depending on what bike and the rotation of the mag When the nut is tightened on the mag it moves it to the "Spot on" position. You'll soon know which way when doing it.

email (option): horror@blueyonder.co.uk

['I'm not really sure what "Spot on" means..']

In the case of ignition timing that's an arbitrary figure decided on by the individual, as no specific tolerance is stated by the manufacturer...

Timing figures are stated as a distance before TDC on the older bikes and are expressed as a fractional dimension (ie 7/16" BTDC)...
Applying normal engineering 'standards' a fractional dimension has a tolerance of + or - .015" so that could reasonably regarded as a guide...

I time my bikes with the head off, using a depth micrometer to measure the piston setting and an electrical 'gizmo' to determine the point at which the contact breakers open...

I find this to be accurate and 'repeatable' and I aim to get the setting to within .010" of the laid down figure...

I know many consider this approach to be 'OTT' but I treat the ignition setting laid down by the manufacturer in the same way I do the piston clearance, bush tolerances, plug gap or any other setting or tolerance...

I go for an accurate manufacturers setting/tolerance unless I or someone else has proved by logical experimentation there is a better alternative...

It is entirely possible that the use of modern fuels may mean an alteration to the timing could be beneficial..

However, the potential alteration may not be the same for all engines or even be necessary..

Therefore, in the absence of accurate experimentation results or the presence of any particular problems I think the original setting is the one to be adhered to.....Ian

email (option): ian@wright52.plus.com

That's the long way to say you do it by the book Ian But there's no way I'm taking the head off every time I do the timing, especially on my ES2 or Manx

email (option): horror@blueyonder.co.uk

['That's the long way to say you do it by the book']..

True enough, but I like to explain my reasoning...It's all food for thought...Ian

email (option): ian@wright52.plus.com

Ian Wright

['That's the long way to say you do it by the book']..

True enough, but I like to explain my reasoning...It's all food for thought...Ian

email (option): horror@blueyonder.co.uk

the last time i adjusted the ignition on my M20 i secured the timing in the middle of the lever on the handle bar, with 2 dots to find the right timing back again, after starting the bike.


I know its is not very accurate, but this timing never is with the tension on the cable and so on.
This allows me to easely change the timing in case the timing slowly changes over the years.