My Briggs & Stratton 20.5 HP mower engine is VERY stiff. I removed the spark plugs, still very difficult. It has had regular oil changes, never run low on oil. Stored in a dry basement. The flywheel can be manually turned with about 40 pounds of torque. It has a small area that is easy to turn. This is an opposed twin configuration. I changed the oil, did not help. Any help would be appreciated.

Does it feel like there is drag or are you coming up to a compression stroke? Is your determination of difficult to turn because the starter is not spinning the engine and you tried it by hand. Remember it is a 20HP engine and is hard to turn.

If it is coming to a compression stroke and stopping you may have a bad compression release. The other thing you may try is adjusting the valves to manufacturers specs 4 Thousands intake and 6 exhaust?

Don

Thanks Dan,
The stiffness could easil be on the compression stroke. I removed the spark plugs and still have the same resistance. I have pretty much ruled out compression as the culprit. It does not feel like a bad bearing in that I cannot feel any "roughness" when I turn it by hand. I will check the valve clearance.
Andre'

How about a belt idler pulley dragging? Remove all belts to engine. It could be the upper journal on the crank does not have a ball bearing and could cause drag if bad.

Don

Andre probably won't need to remove the belts but make sure nothing is engaged and the belts are loose. Valves and compression probably aren't in play if the problem is there with the plugs removed. Without a look its hard to tell but I'm thinking his bearings are seizing up.

Hi Don,
Thanks again, I agree it is most likely bearings. I will start taking it down and let you know the progress. This is a "Flathead" design, so I will remove the heads and look at the valves first. By the way, the belts are loose and the hydrostatic tranny is in the "push" or disabled position.

This is on the money. This works

This is on the money. This works

How do you adjust the valves? I know the specs, just need to know how.