Mower problem:

There was no problem with this machine prior to cleaning. Now it has excessively hard compression.

B&S - 3.5 hp lawn mower - Model # 95902 3137 01 - Code 92101303.
Mower age, maybe 30 years.

This AM I cleaned the engine with degreaser and washed if off. Wiped and dried the engine. (Done this many times in the pase.) Cleaned the air filter and replaced the plug with a new one. I checked the brake system and all the wiring, all operation properly. I've removed the plug to check for excess gas or oil within the cylinder, there is none! I pulled the handle with the plug out and the cylinder and valves move easily and smoothly.

The problem is with such hard compression it feels like the brake is on, but it is not! It's so hard to pull when it gets by the compression stage the rope snaps back with such force it rips the handle out of my hand and won’t continue with the exhaust stage without another hard pull.

Any suggestions?

H.V.Sue, November 2017

Usually, When a lawn mower engine has extremely hard/strong compression, there are three things to check. First, remove the spark plug and turn the engine over. Make sure the valves move freely, and there is no real resistance when you turn it over. (I think you already did this.) Second, leave the spark plug wire off, and try to turn it over. If the compression feels normal, then the issue is probably Your flywheel key. If not, remove the head and gasket, and clean all the carbon off of the head, piston, and valves. Also, make sure the rings aren't leaking oil into the combustion area. When you reassemble the head on the engine make sure you use the right gasket. If the above doesn't work, I've had success by removing some material from the head itself. Use a dremel tool and carefully remove some aluminum from the very edge of the combustion chamber, on the side away from the valves. Anyway, hope this helps, and best of luck!

Zachary Worsech, March 2020