I have an old lawnmower with a 3.5 HP Briggs engine. The engine is worn out
after about 20 years of abuse. It has a 21" blade and the shaft measures
about 2 7/8" to the flat part where the blade is inserted. The blade holder
is attached to the crankshaft with a big nut. I cannot see the threads.
Anyone know if this is reverse thread or regular? I found some new engines
on eBay for cheap but they don't appear to be threaded on the outside of the
shaft. Is it very difficult to find parts to fit a blade onto other kinds
of shafts? I don't seem to be finding any with outside-threaded shafts.
I don't know where to find the engine, but I can tell you a quick way
to tell which way to turn the nut to loosen it:
carefully pull the start cord on the engine and note which way the
shaft turns (may need a helper so one can watch and the other person
can pull the cord). The nut/shaft will be threaded so that the shaft
rotation tightens the nut (otherwise the lawnmower would throw the
blades off every time you started it up).
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