Somehow, I lost the bolt that holds engine pulley belt in place. Replaced bolt and washers, pulley still slips down, which results in lower drive belt fraying. I have a Troy Bilt riding lawn mower.
If the replacement is the correct size, length x diameter x threads / inch and the correct washers with correct torque but still comes out I guess red thread locker is the final choice.
The bolts and washers are the exact size called for in the manual. The pulley shaft is the original that came with the mower. I can easily slide the shaft up and down from the engine. The bolt is tight.
Possibly I'm not understanding the problem but try this.
Put 2 washers on with one wrap of solder wrapped around the bolt between the washers. Run the bolt in and tighten it. Back the bolt out and look at the solder. If it isn't squeezed flat we may be getting closer to a solution for the problem.