Outdoor Power Equipment and Small Engines - Flywheel Key Installation - Old Tecumseh

Newbie working on a Tecumseh 6 HP engine (circa 1978) on an old Ariens rear engine rider. Popped off the flywheel and got distracted so forgot to note correct position of key in shaft keyway. The rectangular key is not of uniform width; the lower portion is less wide (deep) than the upper portion. Two questions: Should the wider upper portion of the key be inserted so it faces towards the shaft or should this wider portion face outwards away from the shaft? Also, how far do you tap the key in? Do you tap it in flush with the top of the shaft or is it normal practice to countersink it a bit?

Thank you for help.

Is this a new key? I don't recall a wedge-shaped key on any tecumseh. Normally, wedge shaped keys have the narrowest spot at the top. Maybe you've got something I'm not aware of though. It might be worth looking at a new key for this engine, because I only know of 2 different tecumseh keys...one is rectangular with a notched end, and the other has a bit of a T shape looking at it from the end and is a bit wider at the lower end, not top. If this is what you've got, then the wideset part goes to the bottom of the key, and it faces away from the shaft.

You put it into the shaft first, then put the flywheel on. No countersinking involved.

Cheese and Billie,

I guess I didn't describe the key well. It is the "rectangular with a notched end" that you Cheese described. I popped the flywheel and reinstalled the key with the widest part into the keyway and the notched end facing downwards towards the engine. Wow, I have spark now! It's amazing what a mess mice make when they live around your engine. Might try to start this weekend if I can fix the leaky gas tank.

Thanks to Cheese and Billie for your help.

Great! Glad you got it. I think I inderstand your description now, but you got it anyway. Good job!