[singleminded]

I think you will have to remove the cover to get the sprocket out of the way.
The magneto should be held down to the platform by 2 bolts and 2 pegs, usually in a diagonal pattern ie: bolt at the rear of mag on timing cover side and bolt on front of mag on the points side .
Try without removing the timing cover but you may have trouble getting the mag high enough to clear the pegs because the sprocket doesn't usually clear the magneto spindle.

[Badgerman]

Just looking to remove the mag and have ordered a sprocket puller from the shop. Silly question but can you leave the timing side cover on and just undo the sprocket via the round hole or do you have to remove the whole cover to get the mag off? I guess it would be easier for access but wondered if it's possible.

Thanks again
James

[Steve_M90]

Following the advice below resulted in success. The nut holding the sprocket in place came free with a sharp tap when wound against the compression. The extractor (from the club shop) worked well except I needed to use a longer metric bolt in the puller. I was lucky in that the magneto shaft had a groove cut across its end so I was able to match mark the pulley. The pulley remained trapped by the cast chain housing.

The reassembly worked well as the match marking enabled me to locate the pulley right first time. I did measure the position of the piston as suggested below (using tissue paper) but with the advance in mid position (didn't read the full instructions!) and found it aligned reasonably well with the matched mark. So I rechecked the set up and found it was as required. I tightened the extended nut against the compression.

The magneto sparked on the first kick over and the bike started once the spark plug was back in the engine.

[singleminded]

you usually remove the nut with the timing chain still on.You should find that fitting a ring spanner and rotating it sharply that the nut will undo,this is helped if the sparkplug is in and the engine rotated backwards against compression. the sprocket extractor should have a bolt in the middle, leave it wound out a fair way before screwing the extractor into the sprocket. When the extractor is in as far as you can get it tighten the centre bolt, sometimes the sprocket will just pop off when you tighten the bolt or you may have to give it a tap with a hammer as Paul has described..When you time the engine I have found it easier to tighten the magneto sprocket first and adjust the point opening with the inlet cam sprocket, I find that there is less chance of the timing slipping when you tighten the nuts this way..John

[Steve_M90]

Paul, Thanks. I follow your method looking at some pictures in another post on the Forum. However, is the first step is to remove the bolt (sleeve nut) and then to use the puller? If so, how do I hold the sprocket or magneto shaft still? (I have a picture but I seem to be unable to upload it)

[phutton]

First thing to do is obtain a magneto sprocket puller. We have them in Spares, so contact Les Hobbs - they a re quite cheap. Screw the puller into the thread in the sprocket until it is tight, then a sharp tap with a hammer on the end of the puller should free the sprocket. Do make sure that the puller is in tight contact with the mag shaft end, not just tight in the thread.

The advance retard is best removed with the contact breaker backplate removed. You can then just unscrew the thimble on top of the mag and out she comes.

Timing on the M90 is 5/8 to 3/4" BTDC on full advance. The normal procedure is to find TDC on the compression stroke (both valves closed) then turn the engine backwards to about 1" BTDC then turn forwards until you reach 3/4 BTDC. You must measure this vertically through the plug hole. Then with a piece of very thin paper (traditionally a fag paper!) between the points, rotate the contact braker onto the cam until you can just pull out the paper. At this point you tighten the sprocket nut. You then check it again. You will probably need a few goes to get it right, but you improve with practice!

Paul

[Steve_M90]

I have a M90 (1932) with MS1-4 Magneto. There is no spark and it's not been rewound so I would like to remove it to enable it to be refurbished. I have access to the holding down bolts and they move. I have disconnected it electrically. However, I'm not sure how to remove the nut that fastens the timing pulley to the magneto shaft.  Also, I'm not sure how to disconnect the advance / retard cable. Finally, how do I ensure the correct timing of the magneto points when reinstalling the refurbished magneto? Thanks