Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
Which engine is it. A bit more info needed.
I'd just drop the old engine and drop another in. Not even necessarily even the same make or model engine. Same hp or similar. I recently swapped the engine on my mini digger from a Honda 5hp to a teschumench 10hp, basically because I found a tesumench 10hp engine on Ebay for £75 that was new old stock, more power seemed a smart move. Most of these stationary engines are fairly generic and a bit of fettlling to swap engines can be way cheaper than doing engine work properly. Next up is dropping a diesel onto my grass mower in place of a worn old Kohler. Tesumench seems cheap engine and parts still seem to be around on Ebay, even if theres a wait for them to come from USA.