Techumseh HM100 10h.p. on Generator

Diesel Dave

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Hello all
I have a generator powered by a 10 h.p. Techumseh. I have really had an issue with the carburetor. At first it ran pretty good but spluttered pretty bad unloaded. I bought one of the $12.00 carbs and it ran even worse. So I rebuilt the old carb with a rebuild kit. Now the generator runs decent at high speed but will not throttle back. It surges and wants to die at idle. Of course it is a generator so there really is not a low idle just a cut back. Also, when I shut it off gas runs out of the carburetor past the butterfly valve. I tried resetting the float to shut off sooner but that did not help. Also, all along you can close down the idle screw all the way and it makes no difference in the way the engine runs. Does this sound like an air leak?
 

jp1961

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Hi Dave,

I seem to recall a YouTube video that said to see if the axle (for the governor buttery valve) has a lot of play in the carb body can cause running issues, however you already tried the new 12.00 carb which didn't improve the situation.

Regards

Jeff
 

cpurvis

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If gas is running out of the carburetor, it still needs work. Probably a new needle and seat.
 

Notdumasilook

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Agreed with Cp..... the needle valve still has issues. It should seal when bowl fills up with gas. Maybe take a careful look up inside that valve once more???
 

Rivets

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As stated, you need to take another look at the carb. When you rebuilt the carb last time, you may have inserted the seat in backwards. Rings need to go toward the carb body, not the needle. Suggest you purchase another kit, part number 631021B, and start over. I rebuild Tecumseh carbs almost daily this time of year, Tecumseh Snow King engines on snowblowers due to fuel left in carbs over summer, and use the following procedure. After rebuilding and installing, use parts of the second procedure to adjust the carb needles.

[FONT=&quot][FONT=&quot]Needle and seat replacement.[/FONT][/FONT]
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[FONT=&quot][FONT=&quot]Remove the carb, and then remove the float bowl. Check the float bowl jet (which is the bowl screw) and make sure the jets both horizontal and vertical are clean and open. Tip the carb upside down and remove the float pin and float with needle attached. Look in the float needle passage and you should see the red float seat at the bottom of the passage. This is where a #5 crotchet hook would come in handy as you need to remove this seat. If you have no hook, but compressed air, you can blow through the fuel inlet and try to pop the seat out. Put your thumb over the passage to prevent the seat from flying who knows where. No air or hook try bending a stiff paper clip to dig the seat out.[/FONT][/FONT]
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[FONT=&quot][FONT=&quot]I would either give the carb a good 24 hour soaking or have it ultrasonically cleaned at this time.[/FONT][/FONT]
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[FONT=&quot][FONT=&quot]With the seat out clean the passage way with carb cleaner. Now you must find a drill bit slightly smaller than the passage way, to be used to press in the new seat. Apply a very, very small amount of a very light lube to the new seat. 3-1 oil or lighter, to help seat it better. Carefully insert the new seat in the passage way with the rings on the seat down toward the carb body. Slowly and carefully force the seat down with the back end of the drill bit. Once it is seated, check to see that it did not flip and the rings are up. Next check to make sure that the float does not have any liquid in it. If it does, replace. If everything looks correct, attach the new needle to the float and install with the float pin centered. It everything is correct, the float should seat level to the carb body, when looking at it upside down. If everything looks good reattach the float bowl, making sure that both the bowl gasket and the nut gasket seal properly. Reinstall on the engine and test unit. Remember to have patience and take your time. Good luck, but I don't think you'll need it.[/FONT][/FONT]
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[FONT=&quot][FONT=&quot]PS: On the side of some Tecumseh carbs you will find a plastic cover. Under this cover will be an idle jet. Remove it and check to see that the jet is open both horizontally and vertically. You should be able to push the old float needle wire through the vertical opening.

[/FONT][/FONT]

[FONT=&quot][FONT=&quot]Adjusting a carb[/FONT][/FONT]
[FONT=&quot][FONT=&quot]Ok, the first thing I would suggest is to reset the armature air gap with the single thickness of a business card, unless you are sure you have a gap of .010 inches. I don't normally recommend doing it this way, but in your case it may be best. Second, this is the procedure I always taught my students to adjust a carb with two fuel controlling needles.[/FONT][/FONT]
[FONT=&quot][FONT=&quot]1. Start the engine and move the throttle control to top speed.[/FONT][/FONT]
[FONT=&quot][FONT=&quot]2. Adjust the high speed needle (this is the one under the float bowl) clockwise very slowly until the engine starts [/FONT][/FONT]
[FONT=&quot][FONT=&quot] to bog down.[/FONT][/FONT]
[FONT=&quot][FONT=&quot]3. Back the needle out 1/8 turn, the engine should now run smoothly.[/FONT][/FONT]
[FONT=&quot][FONT=&quot]4. Now move the throttle control down to idle. If the engine stalls out turn the idle speed screw in one full turn,[/FONT][/FONT]
[FONT=&quot][FONT=&quot] restart the engine and bring the throttle control down to idle. If the engine is running to fast, turn the speed [/FONT][/FONT]
[FONT=&quot][FONT=&quot] screw slowly out until the engine seem to want to die and then in 1/8 turn.[/FONT][/FONT]
[FONT=&quot][FONT=&quot]5. Now with the engine running, adjust the idle needle out until the either gains in RPM's or starts to bog down. If[/FONT][/FONT]
[FONT=&quot][FONT=&quot] the engine gains in RPM's, continue to adjust out until the engine starts to bog down. At this time turn the [/FONT][/FONT]
[FONT=&quot][FONT=&quot] screw in 1/4 turn. Now the engine may be running to fast, so turn the idle speed screw out until you get an [/FONT][/FONT]
[FONT=&quot][FONT=&quot] RPM you like.[/FONT][/FONT]
[FONT=&quot][FONT=&quot]6. Now you must repeat step 5. If the engine bogs down right away turn idle needle back in to your starting point [/FONT][/FONT]
[FONT=&quot][FONT=&quot] and go to step 7. If it speeds up, repeat step 5 again.[/FONT][/FONT]
[FONT=&quot][FONT=&quot]7. Turn idle needle in until the engine bogs down and then out 1/8 turn.[/FONT][/FONT]
[FONT=&quot][FONT=&quot]8. Now the engine should run smoothly at all speeds.[/FONT][/FONT]
[FONT=&quot][FONT=&quot]9. To check, set the engine to idle, then quickly push the throttle control tohigh speed. If it dogs and does not [/FONT][/FONT]
[FONT=&quot][FONT=&quot] come to speed, open the idle needle 1/8 turn and repeat.[/FONT][/FONT]
[FONT=&quot][FONT=&quot]10. Set to go.[/FONT][/FONT]
[FONT=&quot][FONT=&quot][/FONT]
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[FONT=&quot][FONT=&quot]There are 2 reasons I have it done this way is, first the high speed needle controls the fuel going to the low speed circuit and second is that the idle needle controls how much fuel is used when going from idle to high speed. You should also review the section in the manual I posted before starting this procedure.[/FONT][/FONT]
 

Notdumasilook

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I'd love to hear an update. Hope you finally got a good seal at your needle valve. The carb you got,,,, heck I have bought several myself. One was missing a welsh plug and I got creative and actually made one using the bottom of a coke can, a pair of aviation snips, and a tiny gunsmith file. I had/have a sputter/backfire/poof poof issue too.. hence buying new carb instead of a rebuild. I'd like to thank Mr Rivets for his in depth instructions on a rebuild, especially the lil float valve. I've never attempted that but I will next time. But no kidding, if you have time let me know what fix actually worked. might help me fix mine. Wish ya luck!
pssttt ….
I actually went as far as to buy one of the adjustable carbs with the idle screw, the main jet adjustment was the float bowl nut, and had the handy lil spring loaded drain to empty the float bowl. I with that about a day trying to "tune" it but little success.. then knowing this model generator doesn't "idle" went back to the one you have.
 
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