I have an old Craftsman Lawn Tractor with a Briggs 12 hp model 143366202. It was cutting, made a clank and died. I found one of the push rods had come loose. I replaced it and the valves open and close, but the engine does not start. IThe engine spins freely by hand. Don't know if this is related, but there is a small rubber tube that runs into the air filter housing and you can feel alternating suction and blowing while the engine is cranking.

Any ideas? Please be detailed - I have only limited knowledge of engines.

Thanks

The rubber tube is probably the oil breather. Nothing to worry about.

Spark?
Fuel?
Air?

This is where you have to start.

Did you actually do a compression test? With some B&S engines you need to do it in the opposite direction of the shaft rotation.

Thanks for the response!

The engine has spark. I have no compression gauge, but I removed the plug, cranked the engine and felt pressure/suction.

How can I check fuel/air are getting into the cylinder?

When I put the push rod back in place, I had to loosen the rocker arm and retighten. I tighened it down and stopped right before the valve would start opening - is this correct? It is the intake valve.

Air - run without air cleaner

Fuel -
1. Wet plug

Spray carb cleaner into plug opening - listen for a sputter

Don't know for that engine. Usually it would be something like put piston at top dead center until one valve is loose and the other tight. You insert feeler gauge under loose one and check for specified clearance. You loosen and/or tighten until clearance achieved.

You'll have to get an engine manual to get the specs.

Parts & Accessories | Shop & Find Lawn & Garden, Appliance Parts at Sears Parts Direct | SearsPartsDirect.com from Sears lists a repair manual. Home - Briggs & Stratton should have one too. The engine should be 752293a. The engine model # should be on the blower housing. Briggs service manual should cover a number of models.

My dad, a shade tree lawn tractor mechanic in his retirement said that the valves on that particular engine get dirty very quickly and most problems can be corrected by simply lapping the valves. Just what he said. In my retirement, I am learning how to repair my home A/C unit. LOL Anyway, good luck with it.

When you say the engine spins freely by hand, that concerns me. Do you mean with the spark plug in or out? If it is with it in, sounds like you may have a broken rod, or piston skirt which has allowed the piston wrist pin to fall out.

Yes, I did mean that it spun freely with the plug in - I was hoping that there was some sort of compression release. Like I mentioned, I do feel suction/pressure when I take the plug out and turn the engine.

Some briggs engines have a compression release at low speeds. If you spin in reverse, the release mechanism is disabled.