I pulled the cylinder head on the side where I was not getting suction.
Neither valve is broke or sticking. I thought the intake valve could
use a little cleaning. Otherwise, I cranked through the various cycles
and the valves moved properly through each cycle.

I think I will pull the cylinder head on the other side just to do the
standard maintenance of removing carbon and to visually compare the two
sides.

I'll make some calls on Monday to see if someone can test the starter.
I did try jumping directly from the battery to the starter and this did
not resolve the cranking issue. At this point, I am fairly convinced
that the starter is bad.

I learned from my son that he had accidently been cranking the engine
while the blades were engaged. The engine will not start when the
blades are engaged. This may very well have contributed to stress on
the starter.
Ether Jones wrote:
PaulD wrote:

This is an older tractor. I am thinking that some thing caused the
tractor to stall out. Then when my son tried to get it going again he
shot the starter,

This may be the most likely scenario. A "casacading" failure, of
sorts, instead of a single failure causing both symptoms.


...that may have been on its last legs anyway.

Well, it doesn't owe you anything, after 13 years, I suppose.


It is possible that the two problems are related, but they might not be.

Right. There are very few single failures that would cause both
symptoms. The only one I could think of was a valve problem. You have
some qualitative test results which tend to support this hypothesis
("slow" cranking & different puff/suction behavior between the two
spark plug holes), but without quantitative measures it's not very
conclusive.