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Tecumseh 8hp Snow King Tuneup


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  #1  
Old 01-30-2011, 01:55 PM
Frank Martin Frank Martin is offline
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Default Tecumseh 8hp Snow King Tuneup

Is anybody familiar with the correct procedure for tuning the Tecumseh 8hp Snow King engines. In my limited experience with this engine, it is abundantly clear why Tecumseh is no longer in the engine business. I bought this relatively new and not running MTD snow thrower this fall. I rebuilt the carb and now it starts and runs and even throws snow. However, I've never managed to get it to run well. I did my usual bit with the mixture screws. Open them both 1 1/2 turns and then adjust the high speed screw until the engine runs well at speed and then adjust the low speed screw at idle. However, despite all that adjusting it still never ran well. It still misses a lot. Any suggestions?

Thanks,

Frank
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Old 01-30-2011, 04:56 PM
Bill Sherlock Bill Sherlock is offline
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Default Re: Tecumseh 8hp Snow King Tuneup

Frank,

I think your problem is not so much the fault of Tecumseh but rather the result of having ethanol gas left in the tank and carburetor for more than a few weeks. Any Tecumseh engines I've had started and ran flawlessly until ethanol gas came along. Now any engines including Briggs & Stratton and Honda have developed starting and running problems when left for any period of time with ethanol gas in the tanks.

I would recommend going through your carburetor again and spray or soak the parts with CLR and rinse with clear water. Blow dry with compressed air through all passages. Then follow up with a good carb cleaner like "Carb Medic".

Hopefully that will get your engine starting and running smoothly.

Bill
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Old 01-30-2011, 11:24 PM
FarmallBob FarmallBob is offline
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Default Re: Tecumseh 8hp Snow King Tuneup

My experience is same as Bill's: Ethanol gas doesn't agree with small engine carburetors - and especially Tecumseh's. The gas deteriorates quickly and leaves gum/varnish behind. This is particularly so in applications like snowblowers which often sit unstarted for 10 - 11 months at a time.

Recommend THOROUGHLY cleaning the carburetor again. Pay particular attention to a couple items:

1- The impossibly small (like .004") orifice in the brass bowl nut. It runs at an angle from the threaded body OD to the ID near the needle seat. When plugged the orifice is difficult to even find! Use a piece of fine stainless steel wire and run it thru the orifice to push any gunk out of it.

2 - The 2 (or sometimes 3?) idle bleed ports near the throttle plate. They are located under a small welch plug next to the the idle mixture screw. Often the only way to clean the ports is to remove the plug.

HOWEVER before going into the carburetor make sure the engine has a good spark! If you don't get a fat, blue spark when hand cranking, get the magneto back into top shape (and install a new plug) before attacking the carburetor!

----

Tip: When finished using the engine sure to shut off the gas then let the engine run until it quits. The Tecumseh's seem to do best when the carburetors are stored dry.

Good luck! With a clean, properly tuned carburetor the 8 HP Snow King engine will start easily and run nice and smooth.

...FB
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Old 01-31-2011, 02:02 AM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: Tecumseh 8hp Snow King Tuneup

Quite possibly, you are not setting up the carb properly. First, as noted, you need clean fresh fuel, preferably high test, which has less and better regulated alky content. Crap E-10 regular has been found with up to 27% alky in it from the pump. Not good for any engine! Make sure all jets and passages are clean in the carb. The best gum remover I have used is Berkbile 2+2 carb spray cleaner. It will even take off the green gum left by panther piss fuel left in the bowl. You have to give it a minute or two to loosen it up. I do not know of any product that will remove the calcium like deposits left, unless physical removal is used. Like others have posted, the small orifice on the main jet must be clear, as well as the idle and transition ports, or the carb will respond poorly to throttle openning. Check also the throttle shaft fit in the carb body. Any play will allow air to get around the shaft, and will affect mixture and performance. If you have the carb off the engine, remove the fuel bowl and turn it upside down. The float seam must be parallel with the bowl mount flange. Tpp high or low will affect performance. A bad throttle shaft will make for engine hunting (uncontrolled speed changes), due to the throttle not being held in position. Worn linkages will do the same. Make sure that all linkages are not binding, especially the governor arm that is pinned to the cylinder fin near the exhaust. Corrosion there will cause issues.

To set carb: Start and warm engine thoroughly. Open throttle to highest setting. Back out main jet until black smoke just appears in exhaust, or engine breaks up(double strokes). Turn in until engine runs best, THEN back out 1/8th turn. Turn down speed until engine idles. Adjust idle screw until engine idles smoothest, back out 1/8 th turn. Re-adjust high speed as above. Engine should now perform well. The reason for the slight rich mixture is that as the engine is working under load, the combustion process is held in the cylinder under compression for a longer time than if no load is present. If set to run best with no load, the fuel, under loaded conditions, will have burned out before all work performed within the cylinder has been completed. This will cause a lean condition under load, leading to burned valves, and poor performance. Some engines will need even a more rich mixture to perform well, at high speed. On these engines, the mixture is backed out until the engine smokes black or breaks up, then the mixture is leaned (turned in) until the black smoke just clears, or the engine just begins to run smooth, without double stroking. Make sure you have good compression, and that the engine has proper valve clearances. With the crap E-10 fuel, valve wear is a significant problem.

When you are finished working the engine, turn down to idle for a minute or two, before shutting down. This will allow cylinder temperature to stabilize, and will allow the engine co cool down evenly. When finished for the day, turn off fuel, turn engine to high speed, and let the engine run out of fuel, use the choke to keep engine running as long as possible. This will ensure that all the fuel is used in the carb, and will clear out all the ports.

Do not keep partially filled fuel cans more than a day or two, and keep it and all machine tanks full to the top. This will help prevent devolotilazation of the fuel (bleeding out of volotile componants in the gas(iso-butane, iso-propane , alcohol, etc). Gas in a can has to be kept fresh. After 20 days, pour it into the auto tank, and refill. Run equipment at least 15 minutes, weekly, and top off fuel tank. This will keep seals in good shape, will keep most moisture out of the ignition system, and will keep the fuel in the tank fresh.

Andrew
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Old 01-31-2011, 08:49 AM
K D Redd K D Redd is offline
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Default Re: Tecumseh 8hp Snow King Tuneup

It has been my experience that water ANY fuel, ethanol contaminated or not, left to sit in a Tec. carb. for long will cause the idle fuel mixture passage to plug. These passage is VERY small. Most carb cleaners will not clean this area. I got so anger one day I used a band saw to cut-up a Tec. carb. so I could see how it was made. The small hole above the high speed main jet through which the idle mixture flow can be cleaned with Tag Wire if you know where it is. There has been comments one this site about using CLR to clean carb. I have NO experience with this BUT I may try CLR this summer.

Kent
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Old 01-31-2011, 09:48 AM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: Tecumseh 8hp Snow King Tuneup

For those who do not know, the idle supply port is in the main jet assembly, in the adjustable main jet type carbs. The later NON Adjustable units have a different set up. The adjustable jet assembly consists of an about 1 inch long brass tube, threaded also id designed to hold the fuel bowl in place. It should have a gasket on top of the nut shaped part, to seal the bottom of the fuel bowl to the carb. There is a needle, spring, tine brass washer and an O ring, used to seal the needle to the jet body. The needle must be clean, the tapired section free of debris and deposits, and have no imperfections in the needle (scarring or a shoulder worn into the surface from being tightenned too tight) The main inlet is usually drilled clean thru, about .060" in diameter. The main jet, verticle in the tube, should be about .035 in diameter. The fuel adjustment needle restricts this jet for high speed fuel adjustment. The idle supply port is just below the the threaded section of the tube. More often than not, it is blocked with debris of some sort. I use a brass wire brush to clean the surface of the tube, to find the port, and then use a fine torch cleaning tool to clean the port out. A single strand of a steel wire brush will work too. NOTE: this port is drilled at about a 45 degree angle, sloping toward the interior of the jet. More often than not, it is easier to replace the assembly with a carb rebuild kit. You get a new jet assembly, a new fuel needle and seat, new top bowl and bowl base gaskets, and the fuel needle retaining spring, as well as aluminum passage covers (for if you remove the idle and transition port cover).
Andrew
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Old 01-31-2011, 01:39 PM
Bill Sherlock Bill Sherlock is offline
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Default Re: Tecumseh 8hp Snow King Tuneup

Andrew,

Don't believe I've seen the Berkbile carb cleaner around here. For those calcium like deposits resulting from the use of ethanol gas, I've found best way of removing them is spraying or soaking with CLR. Vinegar might work as well but the CLR is effective on light rust too. Once I've got rid of the deposits/corrosion I follow up with a regular carb cleaner which in my case is "Carb Medic".

Back in the good old days before ethanol gas if I had a sticky needle valve from an engine sitting unused for a long period of time like a year or more, a shot of WD-40 into the carb intake and let it sit for a minute or so usually freed it up so dismantling the carb for a thorough cleaning was hardly ever needed. Now as a matter of course when someone brings me a lawnmower it's tear down the carb, do the CLR and carb cleaner thing and replace any diaphragms followed by instructions to the owner to quit using ethanol gas. Haven't had anyone bring me back their mower a second time.

Bill
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Old 02-01-2011, 11:11 PM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: Tecumseh 8hp Snow King Tuneup

Here in NJ, I can find 2+2 in NAPA auto parts stores and Advanced Auto Parts. If NAPA does not have it in stock, they will order it for you.
Andrew
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Old 02-03-2011, 03:07 PM
K-Tron K-Tron is offline
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Default Re: Tecumseh 8hp Snow King Tuneup

You may need to adjust the governor on the engine. I had a HMSK80, and it had similar issues. It wasnt a fuel problem, it was a governor issue. You need a good needle nose pair of pliers, a small flat head screwdriver and I think a 5/32" open end wrench. Once it was properly set, it stopped hunting at idle, and at full rpm.

Unfortunately the engine threw a rod, just like the three other Tecumseh's I owned. Each engine died because my younger brothers do not like to fill my lawn equipment with oil
Yes I know, it was a snow king engine used on a walk behind leaf blower.

I do have a low hour carburetor for this unit, as well as a working magneto.
I did pay over $100 for the carb, but I could let it go for less than that if you really needed it.

Chris
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Old 02-03-2011, 06:57 PM
RSCurtis RSCurtis is online now
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Default Re: Tecumseh 8hp Snow King Tuneup

The adjustment of the governor is an absolute adjustment with the engine not running. The governor hunting is the symptom, not the cause. Perhaps that is what caused the demise of your engine.
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