If you find a junked motor its a good thing to keep the carb and tank and do what youve done then have a good known setup for testing.
Ive got one here but i rarely use it. If it wont go and its got spark, fuel down the carb and if it fires and dies out the carbs got to come off the tank.
Another good thing is a snorkel attachment, then with the metal cover off and the snorkel on (either capped or with a tube on it off to the side) you can degrease and wash the motor and get right in around the top of the carb.
And some of the tanks (i think maybe horizontals) had a fuel cap with a single breather hole in the top of it. One of those with the hole blocked up, then you can tip the mower over and wash underneath without a bit fuel spill.
You said about a 10 series motor with no cover. Thats a later model 4hp. I think its the primer start ones. The older ones are 11ci.
The throttle control on the cover, they used that on those Masports i assume because of the handle and how it folds. Ive also seen the same type on utilitys.
How sloppy is your handle?? I have two here and the handle slops up and down heaps before the mower moves.
One has a white 4hp on it. The other a Tecumseh 2 stroke, id say not original, but it could be.
Do you have a catcher?? Ive got a couple or three here. They had either hard plastic or a metal frame bag type. Both mine came with bag type and i got the plastic catchers the other week. If you search masport on ebay theres a guy with a 2 stroke one on there, its green with a black motor and the brown hard plastic catcher.
I might have a spare front wheel cover here too. Will have to look.
Bob.