You can though it is generally used on water-cooled engines. Run the engine to warm it to operating temperature prior to anything and make sure it has sufficient oil after all is over.
If it has a Briggs and Stratton engine you need SAE30. If it is a Kohler it uses 10W30.
check all belts and chains. if they're intact than you should probaly check out the clucth. it should be right on the main shaft sticking out of the motor.
A typical riding mower with a 38" deck probably comes with a 12.5HP motor. If your mowing requires cutting higher grass or big hills you may want to have one with a larger engine more like a 16.5HP.
Somewhere on the motor there should be a manufacturers plate. Look on that for a model number or other identifying marks and then input that number into a google search.
If it is a 4-cycle engine you definitely need motor oil. If its a 2-cycle engine then the oil is mixed with the gas. If its a reel mower then no oil is needed except for external lubrication. Depending on the engine manufacturer the 4-cycle engines will require either SAE30 or 10w30 motor oil.
which 42" Craftsman riding mower is made by Huskvarna
Replacing the crankshaft requires a complete motor tear-down. It is dead center of the motor. If you have no experience with rebuilding a small engine, you should defer this job to a shop or simply buy a new mower. You won't get a bent crankshaft if you pick up the rocks before you mow.
It just unscrews from the motor
The coil is under the cowling on top of the motor where the flywheel is.
For small motor bike or lawn-mower or similar.
There should be a sticker/stamp an the engine somewhere. It will give you a few specifications about the mower.
There is usually a clutch which disconnects the motor from the wheels. That will make it ok