Yes Jeff it has to be something like that, it just doesn't seem to be able to get it over that last rotation. Only other time you will get a kickback on a standard mower is if the blade carrier is loose or not fitted. This is a different problem but I think it is weight related in the fact that you can't get it spinning fast enough before it hits that last compression stroke. I have never had the kickback on a 24 fitted with a F/C This is the pulley I found, bit expensive though https://www.ebay.com.au/itm/Pulley-Add-On-for-Swp-SB-Air-Conditioning-Chrome-Steel/162694411127
