Small Engines (Lawn Mowers, etc.): LAWN TRACTOR WONT TURN OVER

Question
QUESTION: Hi Eric
I have a Noma 16HP Lawn Tractor with a Briggs and Stratton Engine. The engine model number is:280777 Type:0636A1 Code:9602074B. The problem that has suddenly developed is the engine only turns a few millimetres when I try to start it and it just makes a clonk and wont go any further. the starter is good as I removed it from the engine and ran jumper leads to it from a battery. it spins fast as normal anti clockwise as you are looking down at it from the top of the motor. meaning the flywheel turns clockwise. I tried turning the flywheel by hand and also with a socket and extension bar but it wouldn't turn. so how then coild the starter motor turn it.i can turn it back anti clockwise but not the direction the starter gear attemps to turn it. any idears would be appreciated. also I have tried to track down the manual on the Briggs website without any luck using the model number etc above. you may have ideas about that as well.
Thank You
Barry

ANSWER: Loose rod? Take the spark plug out and see if you can turn the engine.  If it won't turn, remove valve cover and see if the valves are moving.

Service manual:

http://henigins.com/yahoo_site_admin/assets/docs/Briggs_272147VanguardSingleCyli


Eric

---------- FOLLOW-UP ----------

QUESTION: Hi There
       Just to add to this problem. I haven't removed valve cover yet, but have removed spark plug and tried turning the engine by hand. What I have noticed is,I can turn the engine about a quarter of a revolution in either direction before it comes to a dead stop. Refuses to turn any further. Just wondering if this gives you any more ideas before I start dismantling. it makes no difference whether it's in gear or in neautral. The result is the same.
Thank You
Barry

Answer
Pull the valve cover and see if the valves are moving.

The dead stop you are feeling could be something external preventing the engine from spinning all the way around or there could be something inside the engine causing the problem.

I would pull the valve cover and see if the valves are moving.  If the engine still will not fully spin all the way around I would start removing external parts to make sure nothing outside the engine is binding and preventing the engine from spinning.

Eric