classic motorcycle forum

Good call. ?
On a twin, you'd just swap the plug leads over.

But 4 stroke singles don't work like that.

then WIND forward

Aye, if all ye backlashes accumulate, then you may be in no mans land....

Lightly tapping the sprocket onto its taper is highly recommended,
or it may slip or move while you are tightening up the nut.

I was carefull not to disturb crank or timing/cam sprockets ,I did wipe the mag shaft before replacing the sprocket maybe I disturbed the timing then ,
I have set the piston full advance (lever slack cable) at TDC then back 7/16 BTDC watching for the points to just start opening before replacing mag sprocket ,
I am getting a bang back through the carb ,I have the advance /retard at mid way point
if anyone could help me to re time motor I would be very gratefull

yes a piece of "debris" inpregnated into the gasket , now I have a non starting machine, before I took the cover off I marked mag /crank sprockets lining up to the marks I put on the timing case
I feel sure I put back both sprockets as they were when the bike ran earlier in the day before I removed the sprockets /casing 
 I have checked many times the points just starting to open at 7/16 /12mm BTDC then fully open at 12thou just before TDC if anybody could post re timing engine /magneto I would be very grateful  thank you

oil weep problem found I think  bottom screw hole on gasket slight left ?
 now cannot get it to start , when I removed the timing/magneto case I was very careful to keep the inlet/exhaust cams in situ,
 all went back together no problem maybe timing has slipped ,I have points just opening at 7/16 BTDC then full open at 12 thou , I have a strong spark, what have I missed
 all input gratefully recieved
PS I started bike this morning ran no problems