lifters?

It's a Craftsman Lawn Tractor - you might have said that...

I put the number 917271080 into a search engine and got 731 replies. Top of the list was Sears Parts Direct.

Why can't you find the parts you need?
Perhaps the parts are no longer available
Perhaps it's a naming thing - how they're described
Perhaps you're looking in the wrong place
Perhaps you're not trying hard enough

Good Luck...
December 2016