durckelg

I have an almost brand new 8.5hp Tecumseh that came of an MTD with a broken auger gear box. I believe the crankshaft is as trouts2 described. I will check it out when I get home. What state are you located in?

It will work. I have a 524 with a 724 engine mounted on it, no mods. The original engine was the same as the one on the 521.

Do any of you own a 70s or 80s Toro 5/24 or 7/24, if so what are your thoughts?  I currently have one of each, both with very few hours on them.  I purchased them for close to nothing.  I have always been happy with their performance, however I never realized how well they worked until I tried a friend's new Ariens Deluxe 7/24.  Even with the old block tires the Toros dig in plow through the snow, and clean much closer to the surface with their spring loaded scraper.  The scraper and skids were properly adjusted on the Ariens.  I am not knocking the Ariens, it still does a good job.  All three are very difficult bog down, though the 5/24s smaller engine is noticeable.

I have used Seafoam many times along with a brass wire brush clean off carbon inside cylinder heads and pistons.  It works much better than a brush alone, or a brush with carb cleaner. 

I had the same problem with the same mower.  I solved it by replacing the seat.