More random stuff.
Its a good idea to keep spare inlets, plastic ones especially, the covers rub through them sometimes and they break easy.
If you have a mower apart and the tank off, check that the metal tube is firm in the alloy bit on the other end. A tap with the hammer to knock it home if its loose.
Another standard thing i do is check the tension on the two little bolts in the inlet manifold, ive seen them loose and seen them undo themselves and the inlet rattling about. Big lean out. New gaskets can be got easy from a mower shop. The 3-3.5 Hp uses a small one. The 11ci 4hp uses a slightly bigger gasket, its a different manifold. The newer motors (sprint etc) use a plastic manifold thats got a round hole in it.
4Hp 11ci inlet manifold and head are different. The engine cover is longer than a 3.5 by about 10mm or so. And the bracket across the front of the head is a different shape too.
The flag on the bolt on the coil. Sometimes the bolt can dig into the top of the coil and the flag wont flap, i just file it bit off the flag so it will move. Ive also seen the bolts rusty and cruddy.
Keep spare heads, ive had a few where the lug on the top of the head for the cover to bolt too has been busted off or stripped out. And stripped out plug holes, havent had many of them but it happens, easier to use a head than mess about with helicoils etc.
Also keep any of the old pressed steel head gaskets. I subsititue them in for the newer type graphite type that usually de-laminate when you pull the head off. Not sure about different squish thicknesses. Theres different shapes of gasket but they are the same bolt pattern, the gasket relates to the combustion chamber design. Most of the later type with the 'wings' are the chinese Poo and end up in the bin anyway.
The starter sprag body on that motor is a nut, im sure your not meant too, but i undo them with a drift and hammer. Just stick it on a meaty bit and tap away. Remove the flywheel (i do that with a hammer and the weight of the mower which you are not meant to do either) and keep the keyway, beats buying the little suckers.
If its sheared the key, i usually try and spin the flywheel back, with the key spun round it wants to pull through the thread.
Thats about all ive got for now.
