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Hello all..longtime lurker first time poster.

I have an old Briggs Quattro 4hp L-head that is ripping the recoil cord out of my hand. This mower had its blade come off at speed before it was stowed for some years. I expected a sheared flywheel key. Key Looks perfect. I checked to see if the valves moved at TDC and they are tight.

The mower will start and runs if I use a drill on the flywheel nut to start it but can't get it to go manually. Any thoughts on what else it could be?

Numbers are 10A902-2252-E1

Thanks to all.

Camshaft ACR damaged most likely. Even the plastic cam assembly could have parts that slipped.


If I remember correctly I had to replace several these camshafts because the ACR gotten mangled and the engines had severe kickback on hand starting. But I have seen any in the last 5 years mainly because none engines come in the shop now due the customers changing what they use.

You said the blade came off, has the blade been reinstalled. The blade acts like a flywheel, so if no blade it will cause kickback.

Agree with ILengine here. Need a blade and recheck the flywheel key.

Thanks for the replies folks. There is no blade installed so I'll try that next. Before I pull the sump and check the compression release as StarTech suggested, is there anything else that comes to mind? I truly appreciate the time taken to answer this post.

Think you will find, as ILENGINE said, you need a blade on her. That is the main reason you are getting your shoulder ripped out LOL. Torque the blade back on to factory specs. Should be golden.

Yeah, you need a blade. Brings to mind many years ago BIL brought his mower with similar engine. I pulled the flywheel and I could see just a mark on the key. I said there is your problem. He gave my that "You stupid idiot" look snearing. I replaced the key, all was well and he had a different look on his face.

Walt Conner

Finally got my hand on a blade and it did the trick. Thanks to all who replied.