Author Topic: Removing primary drive nuts  (Read 747 times)

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Offline Brooklands

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Removing primary drive nuts
« on: July 24, 2011, 10:31:31 pm »
If you have already disconnected the primary chain/clutch it is sometimes difficult to stop the crank turning when trying to undo nuts attached directly or indirectly to the crankshaft.
To lock the engine detach the rocker assembly or pushrods to make sure the valves are fully closed, take out the spark plug, check piston is some way down the bore, and feed in a few feet of clean stiff cord (sash cord string is good), making sure you keep hold of one end!
As you turn the pinion nut the piston movement will compress the string and become locked, allowing you to unscrew the nut.
You can also do the nut back up in the same way.
The same technique can be used to replace valve springs in situ, without disturbing the head.
Note : If you don't disconnect the valve gear/pushrods and the piston acts against an open valve you could bend the valve stem. If replacing valve springs don't turn the crank from the compressed position unless you want to hear the valve drop into the cylinder  :(
Norfolk 'n good!