Only cranks when spark plug is removed

[Adam22miller]

Came across this issue when trying to start my hawk 250. Replaced the starter solenoid, charged my battery(reads 13.3 vdc) and checked all my grounds. I also replaced the starter thinking it couldn’t overcome the compression. With the plug in it is slow cranking and the moment I remove the spark plug it cranks like it supposed to. What could be causing this?

[Thumper]

The starter should turn the engine faster than normal and constantly (no variation in speed) with spark plug removed.

Do you have a kick starter?