Out of control Tecumseh
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PM me an email address and i will send the Techumseh engine FSM.
I would look at the gasket on the carb bowl. If it is dried out it may not seal, and let air in and screw up how the engine runs.
Parts Tree on the internet sell carb parts.
I took one Tecumseh carb bowl off and found parts to a paper washer that was installed on the bottom of the carb between the jet and the bowl nut. Darn thing just fell apart. After cleaning, put it together without it, and it runs fine, and does not leak.
Also there is a small hole for the idle air just behind the choke plate, if that is clogged it may act up.
The idle screw is located on the side of the carb. You want to remove it while you clean out the idle passage. There are two type of idle screws. The ones WITH the black plastic over them are NOT adjustable, and are installed turned all the way in. The ones without the black plastic cap are adjustable.
You probably should take the carb bowl off and clean it out.
If you had the gallon carb cleaner setup with a basket in a gallon of carb cleaner you could let all the carb parts soak for a couple of days. And then clean it and assemble.
There are some videos on YouTube about rebuilding Tecumseh carbs.
Pay attention to the direction that the hinge of the fine wire little spring for the needle valve is pointing when you take it apart. Some manuals for Tecumseh show that hinge in a certain direction.
Some Tecumseh carbs do not have the plastic seat for the needle valve. If yours is like that just leave it that way.
Purolator inline fuel filter no. F21124 works well as an inline filter to keep small stuff out of the carb. You can get them at NAPA and Advance Auto Parts. If you get one try to get a box that still has the two small hose clamps with it, and install it so the incoming fuel flows into the part of the filter that you can see, so you can see how much dirt is in the filter in the future.
In the future a little blast of WD-40 down the idle air intake hole before storage is a good idea. Some people also temporally remove the carb bowl to get all the fuel out before storage. It will not hurt anything to hit the carb parts with WD-40 when you do that. Kind like the old chicken soup cure for a cold. Won't hurt, and may help.
I have been using RedLine SL-1 fuel treatment for keeping fuel systems clean, and Sta-Bil for fuel storage. You can get RedLine SL-1 at Pep-Boys, and you can get a 100 ml graduated cylinder to measure about 4.45 ml per gallon from McMasterCarr either online or by phone.
Parts Tree on the internet sell carb parts.
I took one Tecumseh carb bowl off and found parts to a paper washer that was installed on the bottom of the carb between the jet and the bowl nut. Darn thing just fell apart. After cleaning, put it together without it, and it runs fine, and does not leak.
Also there is a small hole for the idle air just behind the choke plate, if that is clogged it may act up.
The idle screw is located on the side of the carb. You want to remove it while you clean out the idle passage. There are two type of idle screws. The ones WITH the black plastic over them are NOT adjustable, and are installed turned all the way in. The ones without the black plastic cap are adjustable.
You probably should take the carb bowl off and clean it out.
If you had the gallon carb cleaner setup with a basket in a gallon of carb cleaner you could let all the carb parts soak for a couple of days. And then clean it and assemble.
There are some videos on YouTube about rebuilding Tecumseh carbs.
Pay attention to the direction that the hinge of the fine wire little spring for the needle valve is pointing when you take it apart. Some manuals for Tecumseh show that hinge in a certain direction.
Some Tecumseh carbs do not have the plastic seat for the needle valve. If yours is like that just leave it that way.
Purolator inline fuel filter no. F21124 works well as an inline filter to keep small stuff out of the carb. You can get them at NAPA and Advance Auto Parts. If you get one try to get a box that still has the two small hose clamps with it, and install it so the incoming fuel flows into the part of the filter that you can see, so you can see how much dirt is in the filter in the future.
In the future a little blast of WD-40 down the idle air intake hole before storage is a good idea. Some people also temporally remove the carb bowl to get all the fuel out before storage. It will not hurt anything to hit the carb parts with WD-40 when you do that. Kind like the old chicken soup cure for a cold. Won't hurt, and may help.
I have been using RedLine SL-1 fuel treatment for keeping fuel systems clean, and Sta-Bil for fuel storage. You can get RedLine SL-1 at Pep-Boys, and you can get a 100 ml graduated cylinder to measure about 4.45 ml per gallon from McMasterCarr either online or by phone.
BTW, some people say to use a small steel whire to clean that small idle hole. I would first see if you can spray WD-40 or carb cleaner through that hole, and only use a wire if it is cloged.
Thanks for all detail Jim.
I found very small floaters in the fuel bowl that looked like bits of white plastic -- if this is the same that I found in my other Tecumseh, it is probably clear silicone .
Man, it's hard to believe that a $900 machine didnt have a simple fuel filter from the Techem. boys in WI. I'm headed over to the John Deere dealer to get an inline one.
I cleaned two passages behind choke plate. I unscrewed the brass air screw on side to clean here, and the jet and the main riser tube.
But I didn't find anything in these areas here.
In a little while I'll fire it up.
P.S. Any know the adjustment procedure for the side air screw?
Thanks
I found very small floaters in the fuel bowl that looked like bits of white plastic -- if this is the same that I found in my other Tecumseh, it is probably clear silicone .
Man, it's hard to believe that a $900 machine didnt have a simple fuel filter from the Techem. boys in WI. I'm headed over to the John Deere dealer to get an inline one.
I cleaned two passages behind choke plate. I unscrewed the brass air screw on side to clean here, and the jet and the main riser tube.
But I didn't find anything in these areas here.
In a little while I'll fire it up.
P.S. Any know the adjustment procedure for the side air screw?
Thanks
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Well, the same symptoms here. When you apply the choke it will halfway run-- and no choke it races in that surge. Manifold gaskets are tight and I sprayed cleaner around them to see if there would be a vacuum draw and a difference in run-- but none here. Fuel bowl gasket looks fine.
Either there is massive vacuum leak somewhere or the carb won't deliver out enough fuel.
There is that loud occasional lean misfire pop/bang.
I'll check into ordering an emulsion tube.
Either there is massive vacuum leak somewhere or the carb won't deliver out enough fuel.
There is that loud occasional lean misfire pop/bang.
I'll check into ordering an emulsion tube.
I got it running to where there isn't a race/or surge. On full choke it gives some black smoke, now.
I took out the idle screw again and put 100# air on it from the bottom of the fuel bowl, through the venturi-- it must have dislodged something.
It's 90% there, as it sounds like Harley bike a bit. It has an occasional 'pop' like one, and I believe it is still on the lean side.
I messed up the top of the venturi/ emulsion tube by pushing it down for removal. It took some penetrating oil to lossen and it popped out, but the top plastic is a little deformed. I'm ordering a new one.
Thanks again.
I took out the idle screw again and put 100# air on it from the bottom of the fuel bowl, through the venturi-- it must have dislodged something.
It's 90% there, as it sounds like Harley bike a bit. It has an occasional 'pop' like one, and I believe it is still on the lean side.
I messed up the top of the venturi/ emulsion tube by pushing it down for removal. It took some penetrating oil to lossen and it popped out, but the top plastic is a little deformed. I'm ordering a new one.
Thanks again.
According to the Tecumseh Power Technician's Handbook for 4-Cycle L-Head Engines
Page 16
PRE-SETS AND ADJUSTMENTS
(TECUMSEHPOWER AND WALBRO CARBURETORS)
NOTE: Overtightening will damage the taper portion of the needle. All adjustments should be made with the carburetor in the operating position.
Turn both the main and idle mixture adjusting screws IN (clockwise) until finger tight. If applicable.
Now back the mixture screws OUT (counterclockwise) to obtain the pre-set figure in the chart shown at right.
Tecumseh Power Carburetors
Engine Model----------------------------Main Pre-Set------------Idle Pre-Set
All models with float-type--------------1-1/2 turn--------------1 turn
All models with diaphragm-type-------1 turn-------------------1 turn
Walbro Carburetors
Carburetor Model Number---------Main Pre-Set--------------------Idle Pre-Set
LMH----------------------------------1-1/2 turn----------------------1-1/2 turn
WHG&LME---------------------------1-1/4 turn----------------------1-1/4 turn
LMK-----------------------------------Fixed----------------------------1 turn
EMMISION ENGINES HAVE BLACK CAP ON IDLE SCREW
FINAL ADJUSTMENTS (NON EMMISSION ENGINES)
Start the engine. Allow it to warm up to normal operating temperature (3-5 minutes). Set the speed control to HIGH or FAST. Turn main mixture adjustment screw IN (clockwise) slowly until the engine begins to run erratic. Not the position of the screw. Now, turn the screw OUT (counterclockwise) until the engine begins to run erratic. Turn the screw IN (clockwise) midway between the two positions. This will be the best setting.
Set the speed control to the IDLE or SLOW position. Adjust the idle mixture screw following the same procedure as used to adjust the main mixture screw.
Page 16
PRE-SETS AND ADJUSTMENTS
(TECUMSEHPOWER AND WALBRO CARBURETORS)
NOTE: Overtightening will damage the taper portion of the needle. All adjustments should be made with the carburetor in the operating position.
Turn both the main and idle mixture adjusting screws IN (clockwise) until finger tight. If applicable.
Now back the mixture screws OUT (counterclockwise) to obtain the pre-set figure in the chart shown at right.
Tecumseh Power Carburetors
Engine Model----------------------------Main Pre-Set------------Idle Pre-Set
All models with float-type--------------1-1/2 turn--------------1 turn
All models with diaphragm-type-------1 turn-------------------1 turn
Walbro Carburetors
Carburetor Model Number---------Main Pre-Set--------------------Idle Pre-Set
LMH----------------------------------1-1/2 turn----------------------1-1/2 turn
WHG&LME---------------------------1-1/4 turn----------------------1-1/4 turn
LMK-----------------------------------Fixed----------------------------1 turn
EMMISION ENGINES HAVE BLACK CAP ON IDLE SCREW
FINAL ADJUSTMENTS (NON EMMISSION ENGINES)
Start the engine. Allow it to warm up to normal operating temperature (3-5 minutes). Set the speed control to HIGH or FAST. Turn main mixture adjustment screw IN (clockwise) slowly until the engine begins to run erratic. Not the position of the screw. Now, turn the screw OUT (counterclockwise) until the engine begins to run erratic. Turn the screw IN (clockwise) midway between the two positions. This will be the best setting.
Set the speed control to the IDLE or SLOW position. Adjust the idle mixture screw following the same procedure as used to adjust the main mixture screw.
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I would add that there is a different method. You use an unlit propane torch to add propane gas to the air being pulled into the carb.
When you do this you are substituting propane gas for air, and thus making the mixture richer. The beauty to doing this with a propane torch is that you are not adjusting the carb, and therefore when you remove the propane gas source the carb is right back to where it was before you did anything.
There is a curve as you add fuel to the mix the RPMs increase up to a point and then they fall off as you make the mix too rich. Ideally you want an engine to be just on the lean side of that curve.
So while running, if you add gas from an unlit propane torch, if it is lean it will increase in RPM. If it is rich it will decrease in RPM. If it is set just right, as the gas source starts to get close the RPMs will increase, and as the torch gets closer so all of the gas is going in, the RPM will fall off some.
You can do this for main and for idle.
When you do this you are substituting propane gas for air, and thus making the mixture richer. The beauty to doing this with a propane torch is that you are not adjusting the carb, and therefore when you remove the propane gas source the carb is right back to where it was before you did anything.
There is a curve as you add fuel to the mix the RPMs increase up to a point and then they fall off as you make the mix too rich. Ideally you want an engine to be just on the lean side of that curve.
So while running, if you add gas from an unlit propane torch, if it is lean it will increase in RPM. If it is rich it will decrease in RPM. If it is set just right, as the gas source starts to get close the RPMs will increase, and as the torch gets closer so all of the gas is going in, the RPM will fall off some.
You can do this for main and for idle.
I would replace the black wide O ring bowl gasket with a new one. ANY air leak will cause problems.
Jim , I hope I didnt overwork you here, but that brass set screw was fully seated clockwise. There isn't a spring or a limiter to keep it from moving. It's all the way or nothing.
Sorry, I should have realized that at that time.
This is the only screw. And the jet on the fuel bowl is non-adjustable-- no inside screw.
I 'suspect' some of the "white" debris I mentioned, made its way in this smaller idle circuit--- because the 100# air did the trick.
The venturi tube and jet were clean.
Sorry, I should have realized that at that time.
This is the only screw. And the jet on the fuel bowl is non-adjustable-- no inside screw.
I 'suspect' some of the "white" debris I mentioned, made its way in this smaller idle circuit--- because the 100# air did the trick.
The venturi tube and jet were clean.
Sounds like it is a newer lean burn Emissions carb, but it should of had a black plastic cap on the idle screw to indicate that is non-adjustable.
I am not a Tecumseh teck, just worked on a few engines over the years.
YouTube has some good videos about Tecumseh carbs.
BTW, If your bowl has a raised spot on the bottom, be sure that is under the hinge, so the deeper part of the bowl lets the float move all the way.
It seams that ethanol in gas now days is causing all kinds of problems with small engines.
I use Sta-Bil for storage, but add Red-Line SL-1 when I use the gas to insure that it will not gum up anything. There is a good chance that if gas was on any surface the filim left over will have some ethanol and attract moisture right out of the air.
I remove the bowl to drain all gas and spray WD-40 on the idle air passage way, and on just about any part of the carb I can get it on, then put the bowl back on.
Good Luck.
I am not a Tecumseh teck, just worked on a few engines over the years.
YouTube has some good videos about Tecumseh carbs.
BTW, If your bowl has a raised spot on the bottom, be sure that is under the hinge, so the deeper part of the bowl lets the float move all the way.
It seams that ethanol in gas now days is causing all kinds of problems with small engines.
I use Sta-Bil for storage, but add Red-Line SL-1 when I use the gas to insure that it will not gum up anything. There is a good chance that if gas was on any surface the filim left over will have some ethanol and attract moisture right out of the air.
I remove the bowl to drain all gas and spray WD-40 on the idle air passage way, and on just about any part of the carb I can get it on, then put the bowl back on.
Good Luck.
BTW, one of the problems about posting information, is that it is difficult to tell at what level the reader is at with regard to the subject.
If you tell someone something they know, you insult their intelligence. If you omit something, and they did not know it, they may run into problems that could of been avoided.
If you tell someone something they know, you insult their intelligence. If you omit something, and they did not know it, they may run into problems that could of been avoided.
In the first picture, the round gold item with the indent in the center is called a Welch Plug. There are passages under it that can have particles accumilate. The way to clean it is to punch a hole in the Welch Plug and lever it out. After cleaning you install a new Welch Plug, and then incent the center with a punch to get it to seal in place.
Some of the YouTube videos on Tecumseh carb rebuilding show how to do this.
Some of the YouTube videos on Tecumseh carb rebuilding show how to do this.
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You could also carefully drill or grind with a Dremell tool to get an opening in the Welch Plug to get some tool into an opening to pry it out.
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