Change Drive Pulley On C3 Mower for Better Cutting

[Blueskypilot]

Hello, I just bought a C3 mower for my 48 Cub, which has a 4 inch pulley. Is that too small to spin up the blades? Or do I need a 7 3/4" or a 6.5" pulley?

[tst]

4" is for a sickle bar, put the 6.5 " on it works the best

[Urbish]

Wrong size pulley may affect how the belt enters/exits the sheaves on the mule drive as well.

[KETCHAM]

You want a fast RPM on that mower...larger pulley.....

[Blueskypilot]

Many thanks for the responses. I found the 7.75" pulley on eBay.

[KETCHAM]

That should work fine....let us know!!!!!...get a decent deal????

[JohnMihevic]

Depending on what your cutting with the C3 Mower, the pulley diameter makes a big difference. I have a '48 Cub and bought a new C3 mower in 1973. This came with the 7.75" pulley. If you are doing finish cut, 2' to 3" grass height, it works fine. I use my Cub to cut the "back 3 acres" 2 - 3 times a year. The 7.5" didn't work so well as the Cub engine "bogs" down and I have to lift the mower deck. I bought the 6.5" pulley and it works better in taller grass (more torque, but slower blade speed). I just ordered the 4.5" pulley on E-bay. I believe it will work better if I cut the back field after the grass gets to the height, after 2-3 months.

I don't know the height of the grass you are cutting, If it is pretty tall, I would try your 4.5" pulley to see how it works before getting a new pulley. You will have a lot more torque for cutting tall/thick grass. You will probably need to go in first gear, since the blade speed will be slower.
John