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Small Engines (Lawn Mowers, etc.)/Craftsman 8hp/25 Snowblower Surging


I have an older Craftsman 8hp Tecumseh Snowblower with adjustable carb. I have put a new carb kit in it cleaned it twice, replaced fuel line with a new one,cleaned fuel tank,new gaskets for intake. The muffler glows red on the bottom which I believe means it is running to lean..I have tried all these measures but I can't stop it from surging.Do you have any suggestions how to repair this? Thanks Mike

ANSWER: Check the head bolt torque.  Do you thing someone replaced the carb at some point in time to a too small of carb?

Have you checked the valve clearance and inspected the valve to make sure one of them is not leaking?  You will need a leakdown tester to check to see if a valve is leaking.  You other option is to remove the head and inspect the valves but then you will have to replace the head gasket and you might as well lap the valves since you have the head off.

I'd start by checking the head bolt torque first as I have had some head bolts loosen on Tecumseh engines and cause lean running conditions.


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QUESTION: That was quick.....I don't think the carb was changed. I will check the head bolts,what torque should they be? I have a compression tester that I bought awhile back .....How do I use it? I will check the valves and will get  tool to check clearance  Thanks Mike

ANSWER: Most likely the head bolt torque is 200 inch pounds.  I need the engine model number to verify.

The URL below should take you to one of the Tecumseh engine repair manuals that has the specs.

You can find the Tecumseh service manuals online if the one above is not correct.

A compression tester will not usually tell you if a valve is leaking or the head gasket is leaking...unless they are leaking really, really bad...and then I can usually feel something is wrong just by pulling the starter cord.

Check You Tube for leakdown testers.  This tool is much more accurate at determining if any internal engine parts are leaking.

What is the engine model number?

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QUESTION: I just tightened the head bolts a couple were able to be tightened......I started it and muffler turned red again and surging I don't know the model of engine as there is no label......I can get model of snowblower though its frustrating its a good snowblower and I don't want to scrap its a good blower......I will try the other methods Mike

What model numbers do you have?

Most Tecumseh engine will be a model HSK-xx.  If you look at the service many of the valve specs are .008 of an inch...very common.

I'd pull the valve cover off as it is easy to do and check the valve clearance.  You can set the piston at top-dead-center on the compression stroke just use a drinking straw inserted through the spark plug hole.  Only takes a few minutes and you will rule out valve issues, for the most part, just by checking the clearance.

Send me what ever model number(s) you have.


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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

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