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Need Settings for 86 Tecumseh Carb


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12-21-05, 06:29 AM   #1  
max_power
Need Settings for 86 Tecumseh Carb

I am working on a 1986 Ariens Sno-Thro with a 3.5 hp Tecumseh engine. The model number for this carb is 632378A. It had not been run in 8 years when I got it. I have just Cleaned out the carb so that is runs, but it seems to be running to hot. The muffler turns red and sparks! So I'd guess I have my idle and main screws out of adjustment. Does any body have any recommeded settings for this model?

Thanks!


Last edited by max_power; 12-21-05 at 09:19 AM.
 
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12-21-05, 12:05 PM   #2  
If this is a float type carburetor, the Main Screw should be set 1-1/2 turns out from seating, and the Idle screw should be set out 1 turn. If this is a diaphram carb, both screws should be set 1 turn from seating.

 
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12-21-05, 02:07 PM   #3  
max_power
It's a Float type. That's exactly that I'm looking for. Based off of those settings is is recommended to do any tweeking? For instance I've read that I should set the throttle to idle then turn the idle screw in until it starts to cut out, then turn it out until the engine starts to stumble, then set the screw half way inbetween. After that you turn the throttle up to high speed and do the same proceedure with the main screw. Then try reving the engine from low throttle to high a few times to see if the transition is smooth. If not repeat all steps until it is.

Is this needed?

 
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12-21-05, 03:03 PM   #4  
Official Tecumseh Manual says:

Start the engine and let it warm up ( 3 - 5 minutes) Set the speed to HIGH or FAST position. Turn the main mixture screw in (clockwise) slowly until the engine begins to run erratic (lean). Note the position of the screw. Now turn the screw out (counterclockwise) until the engine begins to run erratic (rich). Turn the screw in (clockwise) midway between these two positions. This is the best setting.

Set the speed control to IDLE or SLOW position. Adjust the idle misture screw following the same procedure used to adjust the main mixture adjustment screw.

Hope this helps! Merry Christmas!

 
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12-22-05, 06:09 AM   #5  
max_power
Thanks James! Sounds like I was doing it a bit backwards. I was adjusting the IDLE first. It didn't seem to go real well. I finally ended up with a setting that seemed to work. Turns out it was almost exactly the 1 turn on the IDLE and 1.5 on the MAIN setting that you gave me earilier. So that must be close. It runs strong all the way through the rpm range. However I have another Issue that I discovered...

When I first started dialing the carb in I was doing it without the air box coevering the carb. (I didn't know the box would effect the settings at the time) I was able to dial it in with a with setting that were about .25 turns richer than recommended. It ran GREAT! When I would lift the throttle lever it would idle up to high rpms smooth as butter.

Then I put the air box over the carb, thinking my work here was done. Not so. I guess the air box restricts just enough air to make a difference, so I had to leat out my setting to the 1/1.5 setting to get good performance.

However, the throttle lever (the lever that is attached by a spring to the lever that is actually attached to the carb) no longer effects the engine idle speed! It just stays in low the whole time. I can reach in and pull the lever attached to the carb and the rpms will jump imediatly. So here is my question:

Is it possible that the spring attaching the two levers on a twenty year old machine is just fatigued? Or could there be something else at play here?

Thanks again! And you also have a merry Christmas!

 
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12-22-05, 07:31 AM   #6  
My guess is that the spring is working fine, because its returing to idle automatically, right? but the cable broke or got disconnected on the lever or somewhere throughout the cable. Check the back of the lever to see if the cable is connected. Sometimes they can come off.

 
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12-22-05, 07:58 AM   #7  
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The way my carb/throttle is set up idle is the default setting. Meaning that if the spring or any other linkage broke the butterfly valve would close.

I am 100% positive there is no other throttle parts that are disconnected. I can see everything and it's all there.

It's just that when I try to open up the trottle with the throttle lever there is no change in idle speed. It just stays at idle speed.

The throttle assembly goes like this:
Throttle lever Spring Throttle connecting arm Throttle linkage Wire Throttle

When I move the throttle lever to the open position the spring just expands, but the Throttle connecting arm does not move. I can reach in and pull the Throttle connecting arm with my finger then it opens up right away. That's why I'm wondering if the spring is fatigued. I just don't know if it should need that much pressure to open or not.

Thanks

 
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12-22-05, 09:53 AM   #8  
You're probably right, its probably the spring. Maybe someone else here can help you out with that. I'm just a 15 year old kid that has rebuilt about 6 small engines in my lifetime so far! Working on a go cart now with a Tecumseh HM 100 with oversize piston, strude honed, intake and exhuast port and polished, etc. I've never owned or used a sno blower, because I live in Vancouver, BC and we hardly ever get any snow?

Whats the model of the sno-thro and the engine? I might be able to find a part # for a spring?

You can usually find the engine model on the shroud.

 
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12-22-05, 10:06 AM   #9  
max_power
Hey James,
Thanks for the help. I have some springs and stuff laying around. I should be able to fix that if that's all it needs. I just want to make sure there's not some other problem that I'm ignoring! Thanks again. I'll repost under a different title as my issue seems to have changed!

 
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12-23-05, 04:23 AM   #10  
mkd55
throttle spring

max! are you sure you are not talking about the governor ?my 8 hp has the throttle cable that goes to a plate then linkage from there with a spring to the carb.something has to open the throttle to deliver more gas? be sure that you don't exceed the limits of the engine rpm's which is 36oo rpm max. check your private messages here i sent you one on carb adjustment. also look at the carb body and find the butterfly shaft and troubleshoot from there. the shaft has to move to open the venturie to supply the vacumn for the carb to deliver more fuel. hope this helps mkd55

 
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12-23-05, 04:29 AM   #11  
mkd55
throttle spring pressure

also to check the throttle for binding just remove all linkage to throttle butterfly shaft and check for ease of movement. carefull though dont spray alot of carb cleaner to free up you run the risk of starting the engine with a dry cylinder and cracking a ring. if it needs lube use wd40 and wiggle the throttle butterfly open and closed to check movement.

 
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