The drive shaft is 1. This engine runs good and does not knock. Has 546 hours on it. Has a new starter on it and new carburetor on it. I also put a new fuel pump on it. There are a couple of the small bolts broke off on the front under the fuel filter. The driveshaft has a knick to ithe metal shown in a picture. I put a little sealant on the underside of the air breather cover around the nut. Does NOT come with a muffler. Was used on a Toro zero turn mower. I tried to put a video of it running on here but I cant but I do have a video of that. The oil will be drained and the filter removed which I can include because it is also new. If picked up I can wait a little while for you as long as it is paid for. That is out of my control.