Small Engines (Lawn Mowers, etc.)/Tecumseh 4hp


My Toro 21" walk behind mower w/ Tecumseh 4hp dies off at high rpms and lacks power to run at any speed.  I discovered oil at the top of dipstick/also oil spatters out when it is run with the fill cap off.  Suspect rings or valves not seating?  Good old mower, but . . .  
If engine replacement is recommended, can you give me cost estimate?

Engine prices vary for some Toro mowers but you may be able to find a new engine from $140-300.

As for your current engine, oil will splatter out with the carb removed...normal.

If I were you I would do the following:

Drain the old oil
Check the dipstick tube o-ring, I'd replace as these wear and can cause a leak
Clean the valve breather.  You will probably have to remove the flywheel to remove the breather.
Check the head bolt torque...seen these loosen on Tecumseh engines.
Refill with new SAE-30 oil.

Test operation.

On of the URL's should be your engine repair manual:

If neither are the service manual for your engine, send me the Toro 5 digit model number and the engine model, spec and serial number so I can look up the manual.


Small Engines (Lawn Mowers, etc.)

All Answers

Answers by Expert:

Ask Experts


Eric A. Jones


Lawnmower Repair . Certified Master Service Technician from B&S. Have 23 years experience on B&S, Lawn Chief, Weed Eater, Echo, Peerless, Wheel Horse, Snapper, Atlas, MTD, McCulloch, Homelite and many other numerous brands. Specialize in electrical repair.


Born and raised in the midwest. Started tinkering with engines when I was about 14 on my Suzuki RM-80. I began lawn mower repair at a small hardware store. I knew absolutely nothing. I read lots of repair manuals and met an older fellow who taught me many lessons. I continued working on small engines through high school and paid my way through college working on mowers at the same hardware store. Decided to get away from the midwest and mower repair so I joined the Air Force. I repaired air traffic control electronic equipment and ended up in Hawaii where I got a part time job at Small Engine Clinic. I gained a lot of experience from the Small Engine Clinic and had a blast repairing small engines. I then took the Briggs and Stratton Master Service Technician test and earned my MST. I then traveled to Wisconsin where I attended the factory update training seminar and received formal training. Continued working on mowers part time as I completed 20 years of military. Retired from the military on a Friday and continued in the lawn and garden industry the next Monday.

MAS Aerospace Operations BA Mathematics AAS Electronic Communications AAS Electronic Technology

©2017 All rights reserved.