Replacing the pulleys would be easier.
Second to that you could sell the 11.5 and dump the money into a new Chinese GX Honda clone 11hp OHV which can be had for $239. The crank will be 1 inch with a ¼ key. It would bolt right on with the only other mod being the belt cover. There’s even a place to hook up your throttle cable from the dash if the 924 is an older model.
If you go for pulling the crank then it’s a lot of work and you should at least put in new rings and lap the valves. You have not done that so would have to at least come up with a valve grinding tool $5-10, compound $4, gaskets ~$10, valve spring compressor $10, ring compressor and expander ~$25 but rings can be removed and installed without these with care $15, and new rings ~$50. Possibly these won’t be available locally so include a few shipping charges. Given the machining cost, rings, other parts and a few tools you’ll probably spend $150 to get the job done.
You’ll have to spend a few hours watching some UTube videos on rebuilding and surf for guidebooks on rebuilding an OHV.
