Setting Ignition Timing

stryka · Post by **stryka** » Sun Apr 08, 2007 8:14 pm

I have an AJS 16 m 1954 350cc single and need to check the ignition timing as I feel it's too retarded perhaps. I remember things like a rod down the plug hole for TDC but I need advice on what setting the advance/ retard lever should be in when resetting the timing and general set up procedure.. I'd greatly appreciate your guidance...thanks,
steve (falmouth)

ajaygray · Post by **ajaygray** » Sun Apr 08, 2007 8:29 pm

The timing on my Alternator one is half an inch BTDC with ignition fully advanced.
How you set it with a Mag though, I don't know.

itma · Post by **itma** » Sun Apr 08, 2007 9:17 pm

do you havea manual magneto or one with an auto advance?

Biscuit · Post by **Biscuit** » Sun Apr 08, 2007 9:39 pm

And do you have the correct magneto for the bike, where does the advance/retard enter the magnet, left or right, looking from the points end. Might sound immaterial but on this depends the position of the handlebar lever for advance.

stryka · Post by **stryka** » Sun Apr 08, 2007 9:41 pm

The bike has a manual advance/ retard lever so I assume it's a manual magneto..

itma · Post by **itma** » Sun Apr 08, 2007 10:45 pm

parfait.
take the end cap off the magneto, kick it over while watching the points move, which way does the lever advance the ignition?
Now find top dead centre, take the plug out and the tappet cover off, engine in 4th gear turn the wheel forward feeling with a screwdriver or rod similar, any thing that won`t fall in!! the piston at full height, on firing stroke, thats the one with both push rods free to turn, and the points in the mag open.
turn the engine over tdc, then back up ..this takes up any slack This ought to be as near as dammit tdc.... mark the rod where it enters the plug hole, then again 7/16 above, turn the engine BACKWARDS, and up again to the top mark, at this point with the lever fully advanced the points should be just opening, use a 1 thou feeler gauge to check.
This is not the most accurate method, but it`ll do to check it, and it`ll run if you set it like that.
also check the points gap first 12 thou, the little bakelite gizmo in there can wear quite badlythink I `ve covered every thing, if not someone will be along to point it out.... can show you quicker than it is to write it.
Why do you think its retarded anyway?
if it kicks on advance its not retarded enough to cause problems

SPRIDDLER · Post by **SPRIDDLER** » Sun Apr 08, 2007 11:52 pm

As That Man said, plus.......

If the cable enters the mag on the right (looking from the points side) then full advance is with the cable under tension. i.e pulled.
If the cable enters from the left then full advance is with the cable slack. i.e not pulled.
You MUST set the timing with the ignition fully advanced in order to get the fattest possible spark.
You MUST check the points gap first. I use a fag paper to check when points are opening. They're as cheap as Tesco's 20/50 and help to keep the points clean too. (A smoker's cough doesn't help though).
If you need to adjust the timing, slacken the bottom sprocket. That is the one on the end of the exhaust cam spindle. I have found this more controllable than trying to set the timing by loosening and moving the top sprocket (on the end of the mag shaft). This may be how every one does it. Anyway I have found it the easiest.
It will probably take you 4 or 5 goes to get it spot on (or more). Mine always seems to have moved after everything has been tightened up (and I could probably get a B.A. in ignition timing singles just from course work).
Mine's a '54 Matchy 350 so match the same as yours.

stryka · Post by **stryka** » Mon Apr 09, 2007 1:00 am

Thanks guys, I've just come back to british bikes after riding japanese for more years than I care to remember.. I suppose I'm suprised at how much I'm enjoying my AJS.. it's well suited to the country lanes of cornwall...

paul knapp · Post by **paul knapp** » Mon Apr 09, 2007 6:13 am

....just one thing with the points, ensure the two contact faces are smooth with NO deposits and square to each other. I too have always used the fag paper method. (legacy of my mistaken smoking youth)... With a gentle pull on the paper, you can easily feel the points starting to open as the points release their grip as the magneto rotates.