My MTD riding lawn mower became almost impossible to crank. Researching the internet I found out that the most likely cause was the compression release pin has worn down on the camshaft. Since new parts for Tecumseh engines are limited I took a chance on a used camshaft off of Ebay. I had already removed the old camshaft from the engine and when I received the used camshaft I measured the compression release pin height above the camshaft. The used camshaft pin was just a little bit taller. I installed the camshaft reinstalled the engine onto the mower and the engine cranks without any problem and is running great. I found an article on the internet how to fabricate a compression release pin from piano wire and I am going give it a go for future use.