still cant get it to start took mag off found pickup had been tracking new pickup still no start using a test plug opened out to over 5mm good spark different plugs tried even it 180 degrees out even tried timing it 11mm after top dead centre has compression and the plug is getting wet I have taken the mag pinion off at least 15 times mag rotating correct is there any classic bike garages in my area I live in north Kent or is it worth taking the mag off and get someone to look at it puzzled thank roger

email (option): roger.beck@node6.com

Roger I know you said it's a previous mag from the bike. But in case of a failing memory, I would still want to check for correct rotation and cam plate. The points block turns clockwise and at full advance, the points close at about 7 o'clock and open again at around 10 o'clock.
The fact that you have a fat spark, but with popping and banging, indicates something amiss with either ignition or valve timing.
If you want to send your mag to me, I'll pop it over to my bloke in the New Forest for a test. It would cost you less than a fiver with 'Hermes'

Ron

email (option): ronpier@talk21.com

Ron you might be right the point rotate clock wise the point just release the ciggie paper at about 11 o'clock and are open at about 12 o'clock so this is wrong as I said before there are 2 notches on the cam plate and the advance cable is notched in the lower of these 2 notches is it easy to move the cam plate because if I move it anti clock wise this might bring it more into line as to what you are saying will have a go tomorrow could email me your address just in case thanks roger

email (option): roger.beck@node6.com

Ron just to add isn't it irrelevant where the point are opening as long as they open with the correct piston position/valve timing

email (option): roger.beck@node6.com

Roger 10-11 o'clock is about right for the fag paper to release. I sort of wish I could be there to help. I'll email my address in case you want your mag checked out. Ron

email (option): ronpier@talk21.com

Roger,

Moving or swapping cam rings or face cams cockup the magneto internal timing. If you rotate a magneto by hand turning it the correct rotation you can feel the pull of the magnets. This is the magnetic flux, the points should just be opening just after the magnetic flux is at its strongest. Swapping cam rings can affect this as the cam rings for opposite rotation magnetos have a different opening time. You will need the mag off the bike for this test, don't forget that the advance and retard will affect this test so full advace points just opening after full magnetic flux.

Tim Walker

email (option): t.j.walker@btinternet.com

Hi Tim,

I had the impressing that it is the type of face cam which is responsible for the operating direction of the magneto and that that is the only difference in a clock or anti clock magneto. this makes the housing and armature universal which should be a great advantage for the manufacturer.

Am I wrong? if so can you shine some light on where the other physical differences are, in the housings or in the armatures?

Regards, Michiel

Hi Michiel,

There are a number of different types of face cam and they will all fit in the Lucas magdyno end plate. Don't forget that AJS ans Matchless use a magneto with this type of face cam fitted and they will all fit the M20. I have a number of old face cams and the advance and retard slot are in different places as are the slotted stop. What i am saying is that to check you have not got a rogue face cam fitted try the test in my post as you cannot alter the position of the magnetic flux but the can alter the position of the points opening to be in time with the maximum flux by changing the face cam.
Hope i have made this clearer

Tim Walker

email (option): t.j.walker@btinternet.com

Hi Tim,

I somehow made the conclusion that there were more differences than I thought. But all clear now, thanks!

Michiel