Techumsa 6hp, backfires and stalls after it runs for 5 mins


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Techumsa 6hp, backfires and stalls after it runs for 5 mins

Jesse Hello,

My father-in-law gave us an older snowblower that he picked up somewhere. It has a 6hp Techumsa engine. It's a Reo snowblower that looks like its from the 70's.

It starts up fairly easy, even in the cold of winter. It has decent power and doesn't bog down as I roll through deep snow.

But after I use it for, say 5 minutes, the engine will start running faster. Not out-of-control fast, but just at a higher speed than when I first start using it.

Within about another minute, it will start back-firing and quickly stall, unless I push the throttle all the way down.

Once the engine gets into that "state", I can start it and it will idle. But as soon as I try to raise the throttle, it starts to backfire. When it backfires, the engine slows down, at which point the governor opens the throttle even more, which causes the engine to stall.

I was thinking that it was starving for fuel, but I tried adjusting the carb for a richer mix and the only difference it made was the exhaust started turning black when it got too rich.

If I let the thing set for an hour to fully cool off, it will start and run again for another 5 minutes.

Any help is greatly appreciated...

Thanks
Jesse

Joe If you have the equipment, do a compression test.
if you dont have the that, take off the cylinder head and look for signs that the air\gas got past the gasket.
Another easy way to find out is while the engine is running spray some water around the gasket and look for bubbles when the engine is running.
Mine (a 60's tecumseh 6Hp) the cyl head warped as it warmed up and replacing the gasket and confirm that the cylinder head surfaces are flat did the trick.

John J Is it a 2 stroke engine. I have a 5.5 Hp snowblower that is 2 years old. According to Warranty dept, they told me the engine needs a short block do to lack of oil in gas. Hopefully this is not your problem. I'm looking to resolve mine and looking for some advise of how I can inspect?? and or pick up a used motor for $50-$75 Any suggestions, or web sights.?
David Thaler
I too have a '64 Ariens sno-thrower in which I rebuilt with a short block. It too is a techumsa 6 hp 4 stroke. Upon completion of rebuilding the short block I ran it and it ran for 5-10 min like a top. I shut down and upon re-starting it the next day it acts exactly like you describe. It idles but starts back firing when throttled up and will not smoothly. I cleaned the carb checked the float and needle valve, adjusted the main jet and air mix screw and still to no avail. My next step is to re-adjust the stator of the ignition sytem to the exact timing specs provided by the manufacturer, If this corrects my problem I will let you know, if anyone else has a better possible diagnostic please let me (us)know.

D Thaler I too have a '64 Ariens sno-thrower in which I rebuilt with a short block. It too is a techumsa 6 hp 4 stroke. Upon completion of rebuilding the short block I ran it and it ran for 5-10 min like a top. I shut down and upon re-starting it the next day it acts exactly like you describe. It idles but starts back firing when throttled up and will not smoothly. I cleaned the carb checked the float and needle valve, adjusted the main jet and air mix screw and still to no avail. My next step is to re-adjust the stator of the ignition sytem to the exact timing specs provided by the manufacturer, If this corrects my problem I will let you know, if anyone else has a better possible diagnostic please let me (us)know.

heiko What is the correct fuel oil mix 16:1 24:1 ?

Thanks

heiko What is the correct fuel oil mix 16:1 24:1 ?

Thanks

Greg Hoffman During a belt change I had to drop the deck of the mower. When reinstall the deck the kotter pin missed the hole. During mowing the deck drop because the fronthinge pin fell out. I own a John Deere RX75. Do you know a website that would sell a unique part like this?
Greg Hoffman During a belt change I had to drop the deck of the mower. When reinstall the deck the kotter pin missed the hole. During mowing the deck drop because the fronthinge pin fell out. I own a John Deere RX75. Do you know a website that would sell a unique part like this?
Tim I have a Techumsa 8hp Ariens snowblower and it consistantly revs up then back to normal. I have cleaned carburator, in hopes to see if it fixes my problem. Sounds like it should. I am having problems getting the float bowl to seat right, it keeps leaking gas at gasket and that is new. Dump question: Should you tighten the float bowl against carburator or hand tighten? I did tighten and still the same...I probably warped the bowl???
Helper My cousins go-cart motor is the same brand and it did the exact same thing take off the air filter and check to see if its wet mi cosins was spitting out gas if the filter is wet replace it and see if that helps if not u may jus have to replace the whole carborator
Terry I would have a good look at the oil pump.
Duke You are on the right trak if you think it's an ignition problem. An engine can only back fire if there is a timing problem. It always occurs on the fourth stroke when the exhaust valve is opening. If the engine is overheating sometimes enough unburnt gas can collect in the muffler and ignite causing what sounds like a backfire but really is not. Start with the magneto it could be faulty after getting hot ... good luck
Murphy it sounds to me like you should just go and rebuild the carburator, replace the head gasket and replace the rings, if that doesnt work replace the points condensers wires and coil. the only other thing i could think of is u might have a warped jug which is causeing blow by when the metal expands. if all else fails email me and ill buy that engine off you..
rob i am having the same problem with my Ariens 724 snowblower, but today after it stalled it was blowwing exaust gas out the carb.I started to tare it apart and found that the intake valve spring seat had broken.I dont know if this was a cause or a result of something else.but i am going to rebuild the whole thing now because pieces of the seat may have made it through the bottom end.
Ian I have a Techumsa 8hp engine that when idoling at hight rpm, starts to rev up then down, up then down. What do I do?

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bob hall Did you install the cold weather baffle to the air box .In the air box there in a red plate that you remove and install over the air intake .
Hillbille Hell try a gas cap the essy way to test is when it starts to quit losen off the cap just a little so that the tank gets air. there is also a small hole down in the carb in under the main jet on the side it is hard to see and find. when a engin sits for a long time it becomes blocked. to clean soke carb in carb cleener or I use YAMAHA combustion chamber cleaner and spray it through. if it is realey blocked I use a acupunture needle carfule not to scratch the inside of the small galery. were safty glasses be gentle and GOOD LUCK THE Hillbille
Bo Martin Jesse I was given a Reo snow blower 10 yrs ago.It had the same problem you discribed. It had been rebuilt about 1 yr before I Got it. When the carb. was reinstalled instead of using the correct gasket, silicone was used instead. I took the carb off and found that the silicone had closed up the intake port about the diameter of a pencil, witch was causing a lean condition witch cuased the engine to over heat, causing it to run poorly after a short time. Just a thought look for something causing a lean condition.


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