Timing Light vs Fag Paper

[Colsbeeza]

I checked the timing today, and found the LHS still lagged behind the RHS by 2 degrees. Given the electric starter, I want it better than that, so replaced the magneto with my newly-reconditioned (Chris Zoch) spare.
After I finished filing, The ATD range had ended up a little wider than I had intended, so the LHS was 2 degrees ATDC on hitting the starter button. Decided to set the timing a little higher at 31.50 BTDC.
I set the new magneto timing at 31.50 BTDC by timing light (Magneto Guys magic box), a little higher than ideal, but well within my comfort range. Tapping the ATD on, it was spot-on first go  (I use a screwdriver to help hold the ATD while tightening the nut as per picture).
I then repeated the check with cigarette paper. Surprisingly, there was only 0.5 degrees difference. But upon measuring the paper, it miced at 0.029mm or 0.0011” or 1.1 Thou (Cols Edit).
So conclusion is the cigarette paper is fine to set the timing, but a perfectionist may add half a degree to his ideal theoretical setting.
A perfectionist may also want to know that the cigarette paper was Tally-Ho, a very old Australian brand, proudly claiming to be Australias Finest (but I note made in Belgium )
Col

[Black Sheep]

Impressive! Mind you, I do wonder just how much these engines ae sensitive to ignition timing. You certainly notice if they are over advanced but a couple of degrees retarded doesn't seem to make any significant difference. The old stick down the plug hole certainly seems to work for low compression engines. 

[bikerbob]

I agree I think we sometimes tend to rely to much on modern timing devices which did not exist when these bikes were built. Does anybody know how they did the timing in the factory whilst I use the old fag paper system I can't imagine they did that back at the factory. You often see old videos of bikes being assembled at the factory but I have never seen one showing them doing the ignition timing.

[Rex]

The Comp shops of Norton, Velocette, AMC etc certainly used degree discs etc, but you can bet the cooking model's production lines used nothing more sophisticated than a calibrated pencil..

[muskrat]

G'day Fellas.
On my bikes I have to use a strobe as both have Boyer. Back when I had a mag on the plunger I'd use a fag paper to get it close and then use a strobe to fine tune.
My plunger being low comp isn't as fussy with timing but the high comp/high octane Cafe will notice 1 or 2 degrees either way.
Cheers

[bikerboy]

I often wonder because I use the old lolly stick and a feeler gauge. Either I am fantastic at it or the engines dont care if they are out a little bit because they always seems to run about the same. I normally wedge a wooden garden peg in the ATD, a feeler gauge in the points and give the ATD a whack to seat it.

I will confess I normally set the piston height before I put the cylinder head on so that I can at least get that accurate with a depth gauge.

[Colsbeeza]

Black Sheep,
 

You certainly notice if they are over advanced but a couple of degrees retarded doesn't seem to make any significant difference.

Orabanda's work on the dyno showed best torque at 30 deg BTDC for iron heads, well below the book settings. So correct!
Col

[RichardL]

I don't trust myself with "feel" either with a fag paper or with a feeler gage when it comes to judging nothing versus next-to-nothing. I've mentioned here before, I've taken to attaching a clip lead to the fag paper as a small weight that falls to the floor when the paper is released by the tiniest amount of opening at the points.

Richard L

[Colsbeeza]

RichardL, Not a bad idea. Trying to pull the fag paper whilst trying to rotate the crank slowly took a few tries to get it right. I needed three hands.
I have always thought we should have been born with four arms.
An interesting discussion here - https://www.britbike.com/forums/ubbthreads.php/topics/417682/re-ignition-timing.
Seems my 0.5 degree lag using the fag paper is about right.
Col

[Worty]

I like what Bergs has done with my maggie.  He got the mounting holes machined out a bit so the whole unit could be moved a fraction to advance/retard.  The idea is that you get the timing as close as possible, see how she runs, then fine adjust by moving the maggie.  I've tried scores of times to set the timing, often with very good results, but having the option to make fine adjustments without having to take the timing cover off, release the ATD, and set btdc seems an excellent idea.

[Topdad]

My very fist A10 plunger was helped back on the road by a friend who loved messing about gizmos ,he worked in L-pool Uni electrical lab  and made some weird things one of which was a strobe timing light ,I didn't have a timing disc but he'd set it up with marks on the chaincase ,Ithink ,bear with me it was 57 yrs ago. just plugged into one ht lead and it worked well .Being young and seeing how easy a fag paper was, the timing light was little used and lost . I must be quite good at it as my bikes have always been reliable runners but hey oh I may poss consider using one .

[WozzA]

My very fist A10 plunger was helped back on the road by a friend who loved messing about gizmos ,he worked in L-pool Uni electrical lab  and made some weird things one of which was a strobe timing light ,I didn't have a timing disc but he'd set it up with marks on the chaincase ,Ithink ,bear with me it was 57 yrs ago. just plugged into one ht lead and it worked well .Being young and seeing how easy a fag paper was, the timing light was little used and lost . I must be quite good at it as my bikes have always been reliable runners but hey oh I may poss consider using one .

Stick with the FAG paper Bob
You know what happens with you & Electrickery   

[Slymo]

I've always found that the devil is in the re check. Setting the timing with a stick down the plug hole and a fag paper is pretty much ideal for me. There is bugger all interpretation to be made and as long as the cam ring isn't shagged and the mag is in good order all should be fine. However as I discovered the final tweak on the mag drive sprocket nut would shift the setting back to where it had been before I adjusted it way too advanced. Driving the sprocket onto the taper with a drift fixed it in the end but it was a lot of shagging about. Being a Super Rocket it has a manual advance so I can always give it a tweak mid ride if I approach a  particularly steep hill. Been good for timing for years now so can't complain.

[Black Sheep]

Don't forget to check on both cylinders. As a feckless yoof I didn't on my Dominator and holed a piston. Discovered that one cylinder was at 32 degrees btdc, the other at 52 degrees...

[Worty]

Don't forget to check on both cylinders. As a feckless yoof I didn't on my Dominator and holed a piston. Discovered that one cylinder was at 32 degrees btdc, the other at 52 degrees...

I only ever did one cylinder, and got away with it.  Are you supposed to take an average of the two??