Ignition timing.

nnnrh · Jun 24, 2014

Just had a quick look with a stroboscope at the ignition timing, found there was two marks on the rotor about 3 eighths of an inch apart. how do you tell which is the correct one and with a Boyer type ignition, how do you adjust it???????

Hobot · Jun 24, 2014

If running then put the light out and creep up and down timing by slight tweaks of the boyah trigger plate till it tends to back fire on kicks then retard a bit so it just don't then put on the light and mark the mark that's most appropriate but don't put any numbers in mind until you have put time scale on crank and indexed the factory dial gage. IIRC boyah trigga plates have two marks so other lessor British twins can use it too. As running to picked the right one to fine tune now and somehow mark or go though similar tedium time and time again.

Player#3 · Jun 25, 2014

Hi,

I used a strobe yesterday and made this bad video of it.

You can just about see the marks I made with static timing using a TDC finder first.

But as Hotbot said you basically adjust the Boyer timing plate a few degrees to find the sweet spot.

Regards,
Sean

L.A.B. · Jun 25, 2014

nnnrh said:
Just had a quick look with a stroboscope at the ignition timing, found there was two marks on the rotor about 3 eighths of an inch apart.

Could one of those 'marks' you are seeing actually be the edge of the raised timing pad?

nnnrh said:
how do you tell which is the correct one and with a Boyer type ignition, how do you adjust it???????

There should only be one timing mark on the raised pad (note there are usually two pads/marks 180 degrees apart but the other pad/mark can be disregarded).

Note that a Boyer is set to 31 degrees BTDC @5,000 RPM. Slacken the two pillar bolts and rotate the Boyer stator plate to adjust the timing. Moving the plate clockwise advances the timing.

nnnrh · Jun 25, 2014

I will have another look Lab, maybe that was what I was seeing, it was a bit rushed. The Mk 3 workshop manual says on later models there are 2 marks. I don't know if it referring to later mk3s or just later commandos in general.{ mine is a MK3]. thanks for the help, I will let you know . cheers

L.A.B. · Jun 25, 2014

nnnrh said:
The Mk 3 workshop manual says on later models there are 2 marks. I don't know if it referring to later mk3s or just later commandos in general.

Yes, the MkIII manual states that "The latest Lucas rotor has two timing marks opposite each other" and does mean the additional pad/mark usually found on the later Lucas rotors from around 1971, not just those fitted to the MkIII.

Deets55 · Jun 25, 2014

I only have experience with a MKlll and not sure if this applies to all Norton engines. Try going to TDC of compression stroke on either cylinder. Look through the inspection hole you should see the pad and the timing mark. Get some red paint or nail polish and mark the timing notch. I use a tooth pick to apply the paint. Give it a little time to dry. Then go thru normal timing procedure. After setting timing to 31 degrees @ 5,000 rpm look at timing at idle, you can use this a as reference if you pull you Boyer off again. Hope this is helpfull.

Pete

nnnrh · Jun 26, 2014

yes thanks guys, I was looking at the edges of the raised tab, they initially were more visible than the actual timing mark in the middle. when work gives me a day off II will get back to it with the timing light, and see just where my soon to be painted timing mark is.

Hobot · Jun 26, 2014

Seasoned servicers soon learn to only only by which set of valves are loose and which are tight to ID which jug is on ignition phase of up stroke or end up reversing trigger leads or breaker points too dam often.

acotrel · Jun 26, 2014

I believe some people actually shine timing light on the Boyer pickup when setting the timing ?

Old Bloke · Jun 26, 2014

I know I am stating the obvious, but I found it helps to make sure the timing mark is clearly marked. I tipexed the raised bit white, and ran a black marker pen along the timing mark, and when it's being timed, it's very clear.
Peter

Hobot · Jun 26, 2014

Time lights may mislead ya until crank degree wheeled indexed to calibrate true TDC and factory dial. These are organic life-like machines so best results by fine tuning beyond just look up, set and forget, so time light only useful after the best initial setting is found. If kicks back on starts then bit too advanced, if it don't could mean its more retarded timing than needed so dulls toque hits some. My Combats like 29' but spit & strike back if approaching 30'. I mostly run 91 octane.

nnnrh · Jun 30, 2014

Thanks for the help, yes the 2 ends of the raised part actually look like the timing marks, until you realise what is going on. And yes who ever set the timing on this bike had fallen into the same trap, one of the these erroneous marks had been set as the 31 degree position leaving the ignition rather advanced. This explains the pinging ever time the engine was under a load, and also the kick backs when ever I tried to kick start it. All good now, engine feels smother and the new battery has alleviated the need for kick starting, so happy biking again.

Biscuit · Jun 30, 2014

hobot said:
Seasoned servicers soon learn to only only by which set of valves are loose and which are tight to ID which jug is on ignition phase of up stroke or end up reversing trigger leads or breaker points too dam often.

Or stick you whoo-whoo finger in a spark plug hole to feel for pressure as you turn the engine. :mrgreen:

Hobot · Jun 30, 2014

Ugh finger pressure sensing has mis lead me oppositely more than once on two Combats with some cam over lap so my habit now is not to waste time but verify spark stroke side by valves definitive method. May work a treat on standard cams.

Ignition timing.

nnnrh

Hobot

Player#3

L.A.B.

Moderator

nnnrh

L.A.B.

Moderator

Deets55

nnnrh

Hobot

acotrel

Old Bloke

Hobot

nnnrh

Biscuit

Hobot

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