I have an old Suffolk Punch 35. There is no spark at the plug. I have taken the flywheel off and there is a lot of oil in and around the magneto. The inside of the flywheel looks worn as if it has been wareing away on the magneto. There is a very weak spark from the HT lead to the head if I remove the spark plug cap from the HT lead. The magnets are attached to the flywheel via two screws. Do the magnets ware away, hence a weak spark. Any suggestions of what to try next would be appreciated.

Thanks