Tecumseh TCII (TC200) 2102C throttle plate


Why do I get myself talked into these things? ;-)
Bit of a long shot that someone else has one of these, but I've got an old 10" tiller with a Tecumseh TC200 2102C engine on the bench (the tiller says 'Dynamark' in one spot, and "Noma" in another, so I'm not sure who the manufacturer is; Google returns basically nothing for either).
The machine idles OK, but was struggling under load. I noticed that the throttle plate wasn't opening all the way - if I held it open manually, the engine would run at a healthy rate.
The carb on this thing is a tiny Tillotson HU. The engine has a vane governor, and a spring connecting the throttle cable to the governor mechanism. I'm reasonably confident that this spring has gone weak or stretched (the throttle plate itself can be moved perfectly by hand without resistance), explaining why the throttle plate doesn't open all the way when the throttle is squeezed.
However, there's no separate spring for returning the throttle plate closed when the throttle is released; I'm wondering if there should be, and it's gone missing over the years - or is the governor vane supposed to also close the plate all by itself when it's not fighting against the tension of the spring at the end of the throttle cable?
(I can hunt around for a replacement spring, or even - ugh - hack things by shortening the existing one, but it'd be nice to know whether I'm also missing a return spring on the carb side of things)
cheers
Jules
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On Thu, 03 Jun 2010 21:20:37 +0000, Jules Richardson wrote:

Should be a return spring of some kind. The vane should only pull the plate open as the push on it diminishes with the reduction in engine RPM. The Lawn Boy carb i just repaired has a spring coiled around the top of the carb where the plate shaft connects to the throttle mech and governor.The plate's position depends on spring tension applied to the vane by the throttle spring and the tension the vane returns. Sort of a balancing act. The throttle shaft on this particular carb tends to seize up after a couple years. They want $50 for a new carb that was redesigned but if the shaft is removed and lubed and the two manifold mounting bolts not tightend in excess as to warp the plastic carb body it's fine for another couple years. This a 2 stroke 6 horse motor.
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Jules Richardson wrote:

Shorten the spring, I've done it. Just a little at a time though. I usually cut it off and unwind one coil, straighten it, make a hook on the end and hook it up.
--
LSMFT

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On Thu, 03 Jun 2010 18:10:58 -0400, LSMFT wrote:

Yeah, I think that's where I'm headed... I bet this tiller is well over 20 years old, so it wouldn't be at all surprising if the spring had lost tension.
There are actually two spring holes on the governor vane - I can't recall without looking which hole the spring's currently in, but if it's in the 'nearest' one I'll try moving it to the other position. I know the previous owner had the carb off, so it's just possible they reassembled it with the spring in the wrong spot.
cheers
Jules
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On Fri, 04 Jun 2010 12:23:27 +0000, Jules Richardson wrote:

... and that's fixed it, just for the record. I should really look up what the max rpm for that engine is and find a way of measuring this one though; it sounds like it might be running a little too fast now if anything (although it has an impressive amount of power now for something so small).
Turns out the neighbor has one just like it which runs but has a jammed clutch, so now he's bringing that over for me to take a look at some time. It never ends ;-)
cheers
Jules
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replying to Jules Richardson, scott wrote:

What did you find out about the springs? I am having the exact same problem as you. I am thinking there should be a return spring
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I've got a spring assortment, some where. From when I tried to get into small engine repair.
If you copy all the numbers off the engine, and take the old spring. A Tecumseh dealer probably sell you a new spring for under five bucks. Hardly worth the worry.
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Christopher A. Young
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On Jun 3, 5:20�pm, Jules Richardson

The governor is suppose to keep the engine running at a certain RPM. If the load increases, the governor will open the throttle plate to allow more fuel to create more power and the rpm selected by the use of the throttle. If everything is working well, the throttle plate will return to the closed position only after the throttle is shut down. The throttle plate should only open fully when the engine is under heavy load.
Is your throttle cable adjusted properly? This may be your problem.
Hank
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