Tecumseh Carburator

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  #1  
Old 07-18-05, 07:00 PM
Ray Scott
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Tecumseh Carburator

Just finished cleaning up an older murry wit a 10hp Tecumseh engine.

Wants to start but won't.

Cleaned the carb appears that all the jets are clear.

Set the (high?) needle at 1 1/2 turns out

Set the bowl needle at 3 turns out

After numerous install/remove sequences I noticed I wasn't getting fuel into the bowl.

Fuel IN port is clear, float needle valve clean.

It looks like the float is hitting the bottom of the bowl, therefore pushing the needle valve up, closing off fuel flow.

What adjustments do I need to do to get the bowl to fill, also what is the orientation of the bowl to the carb body?

Ray
 
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  #2  
Old 07-18-05, 11:49 PM
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When the float drops to the bottom, it should let the needle fall downward and allow fuel to enter the bowl. If it does not, then the fuel inlet, filter, hose, or outlet at the tank is/are clogged.
 
  #3  
Old 07-19-05, 06:53 AM
Ray Scott
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Tecumseh Carb/now running poorly

Thanks Cheese,

I've checked all of those things. No clogs.

I took the bowl off and moved the float manually. I could turn on, shut off fuel as it should with the needle valve.

I believe the float is bottoming out when I put the bowl on. Then the float is putting pressure on the needle preventing fuel flow.

What do I do in this case?

Ray

Got the sucker to run.

Unfortunately lots of black smoke/loping and some backfiring.

Adjusted needle from 3/4 out to all the way in to almost out. NO affect.

Adjusted bowl needle all the way in wanted to stop. Moving out symptoms got worse.

When I had it adjusted to minimum symptoms and tried to engage blade engine bogged down and would quit.

Ray
 

Last edited by Ray Scott; 07-19-05 at 08:21 AM. Reason: Update
  #4  
Old 07-19-05, 09:02 AM
Azis
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If you made any adjustments to the float level, it sounds like it may be too much. On the float where the needle hangs is the tab to bend to adjust the float level. The needle should seal and stop fuel flow with the float about level with the base of the carb.
It sounds as though your adjustments are counteracting for too much fuel allowed by the float/needle and seat. When you add the load to it, it may have enuff fuel but not properly mixed with the right amount of air for proper combustion.
I think initial settings on both screws would be 1 1/2 turns out.
 
  #5  
Old 07-19-05, 09:25 AM
Ray Scott
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Tecumseh Carb

Azis,

Thanks

I did not adjust the carb float, I just cleaned it real good and reinstalled.

First two installs I got no fuel, (see first post). Last install needle set better .

I know I'm getting fuel now. I'll try the new adjustments. I figure it is just a matter of getting the proper fuel/air mix. Just need a good starting point.

How does the bowl screw affect fuel flow??

Ray
 
  #6  
Old 07-19-05, 07:24 PM
Azis
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  #7  
Old 07-20-05, 08:34 PM
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Ray Scott,

The bowel screw that you referrer to is the main screw jet. This screw will ration fuel up from the bowel through the emulsion tube into the venturi (by low pressure created from the piston) where it will mix with air to form the air/fuel mixture at high engine speed.

By adjusting this screw downward (at full throttle) you will allow more gas into the mixture for a richer burning engine. Upward will allow for a leaner burning engine. If everything is right,(no air leaks) or mechanical problems, the sweet spot will be in the center of rotation.

The Idle screw will ration fuel through very tiny holes that are located in front of the throttle flap. With the throttle almost closed these holes allow enough fuel beyond the throttle flap to maintain a low engine speed. When the throttle is opened the air flow by the main jet will take over the fuel supply. There will be two adjustments. One for the high speed (main jet) and one for the low speed (idle jet).

All these adjustments are per no vacuum or intake leaks.


God Bless,
Dave237
 
  #8  
Old 07-21-05, 09:00 PM
Ray Scott
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Tecumseh running poorly

Thanks to everyone for the help and advice.

I got the carb cleaned and reinstalled. No local source for a rebuild kit.

The motor will start but I can't get it to run right.

Throttle lever on choke, motor starts but I get some serious backfiring.

The mixture screw will kill the motor when turned in too far our out too far, (1/8 turn at a time) the backfiring keeps happening. Backfires seem more severe with needle moving out.

Idle screw has no affect.

Someone suggested I might have a sheared flywheel key.

Any more help would be greatly appreciated.

Ray

AZ thanks for the link!
 

Last edited by Ray Scott; 07-21-05 at 09:01 PM. Reason: add info
  #9  
Old 07-21-05, 11:37 PM
Azis
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It does sound like the shear key could be sheared. The manual should have all the steps for replacement. A puller will be helpfull. Other than that it is fairly simple. Almost certain you will need to pull the flywheel to inspect the key.
 
  #10  
Old 07-21-05, 11:49 PM
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Sounds to me like the carb needs work and is probably flooding. Is there gas in the oil? Gas dripping from the carb?
 
  #11  
Old 07-22-05, 04:55 PM
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I agree with Cheese. Just had a Tecumseh carb that the throttle shaft was worn on. Before a total rebuild it would back fire through the carb due to a very rich mixture that would ignite to early.

I would first rebuild the carb before pulling the flywheel.

God Bless,
Dave237
 
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