well to hone the bores you need the pistons out so it has to be removed to do so. yes the bonnet and air cleaner have to come off to get it out.

if you can rock it side to side it might have a busted magneto gear remove it and check. if it isnt broken or bent the shaft its something else remove and dismantle the pony to find out why. before dismantling see if you can turn the pinion shaft by hand or if it does a full rotation by turning the main engine(if the pinion is engaged that is) all the gaskets are available from the dealer. so are piston rings, bearings and crank seals. carb kits are also available.

gwoods, thank you for the possibilities about d4 7u pony motor/7u11300. I now have looked inside pony motor. There was a build up rust in one side of motor. One of the valves was believed to be weak and I have got a replacement. Honed the cylinders and have ordered a new gasket for pony motor block. I have got pinion lever freed up. Thanks for help