Tecumseh HM80 How do you lower rpm's ??

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  #1  
Old 09-25-05, 07:18 PM
TheKneebiter
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Tecumseh HM80 How do you lower rpm's ??

Hello,

I have a Snowblower with a Tecumseh HM80 engine and when I move the throttle to full it is revving to high. I need to lower the rpm's when I run full throttle. What is the correct way to do this ? Thank' in advance for any help
 
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  #2  
Old 09-25-05, 08:37 PM
cheese's Avatar
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Do you have a manual? You'll need to adjust the governor. A manual is available at cpdonline.com
 
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Old 09-26-05, 03:41 PM
TheKneebiter
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I do have the manual but it shows so many different configurations that I am lost. I did see my carb on there and it shows a high speed rpm adjustment screw and an idle speed crack screw. Would the high speed screw lower my full throttle rpms ? In manual 692509 My carb is on page 36 box/picture 23. Thanks
 
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Old 09-26-05, 06:30 PM
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Unless it is causing potential engine damage/wear, I wouldn't slow the engine down as the slower it is running, the shorter the distance it will throw snow.
My $.02 worth,
Mike
 
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Old 09-26-05, 07:00 PM
TheKneebiter
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an over revving engine will fail sooner or later. i want to slow it down to where it should be. anyone know what i need to do to slow it down ??
 
  #6  
Old 09-27-05, 05:03 PM
TheKneebiter
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Originally Posted by mla2ofus
Unless it is causing potential engine damage/wear, I wouldn't slow the engine down as the slower it is running, the shorter the distance it will throw snow.
My $.02 worth,
Mike
First off I fixed the problem. Like Cheese said it was the govener needing adjustment. As far as letting an engine on a snowblower over rev thinking it will throw the snow farther I think you are mistaken. The machine is only supposed to rev at a certain rpm when there is no load on it. When you push it into a snow bank or deep snow the engine starts to feel the load and the govener forces the the engine to full rpm. So under load full rpm is ok but no load high rpm = rod through the block. Now I think that is correct but I could be wrong. So if I am someone please explain it so both of us will understand. Thanks for the tips.
 
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Old 09-27-05, 05:27 PM
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TheKneebiter,

Like your name.... You are correct! As you may have already found, there is a control lever between the carb throttle and governor control arm anchored by a spring. You can bend the control arm to increase/decrease RPM's.

God Bless,
Dave237
 
  #8  
Old 09-27-05, 07:23 PM
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Kneebiter, in my post I said "unless it is causing potential engine damage/wear". I meant keep the governed speed high but below the point of damage/excessive wear.
I disagree with your understanding of governor opreation. A governor keeps an engine at "X" maximum rpm regardless of load until load exceeds power output of engine. At that point engine speed starts decreasing.
My apologies for misleading you,
Mike
 
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Old 09-27-05, 07:34 PM
TheKneebiter
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Originally Posted by mla2ofus
Kneebiter, in my post I said "unless it is causing potential engine damage/wear". I meant keep the governed speed high but below the point of damage/excessive wear.
I disagree with your understanding of governor opreation. A governor keeps an engine at "X" maximum rpm regardless of load until load exceeds power output of engine. At that point engine speed starts decreasing.
My apologies for misleading you,
Mike
I think you have the thought that a governer stops the engine at a certain rpm. This is how it was or is on mini bikes and gokarts. You can govern the speed so the engine will only go so fast that way your kid does not end up in a tree. But with snowblowers I would have to disagree with you. The governer holds the engine at a certain rpm untill load. Lets say the max rpm of the engine is 3000. The governer would hold the engine at say 2000 rpm at full throttle untill it feels a load from heavy snow then the governer would pull the throttle full to give you the 3000rpm. If the engine was to run at 3000 rpm without a load it would throw a rod. If you listen to your engine when you are blowing snow you can hear it surge and rev as soon as you hit the heavy stuff. So on snowblower not only does the governer hold the rpms down it also revs them up as where on a minibike or gokart it just holds it down to a set point. Am I rambling ???
 
  #10  
Old 09-27-05, 10:53 PM
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Governor

The governor, as pertaining to a yard machine, is a very delicate and artistic (spring loaded), feed back device. It is designed to maintain one and only one certain speed, no matter the load or lack of it.

An increasing load will begin slowing the engine which in turn actuates the governor lever to increase throttle input not to increase RPM's but to maintain the preset rpm's no matter the load, be it heavy or light. If RPM's increase beyond the preset limit the governor will react in the opposite direction by decreasing the throttle to slow the engine.

You can try it.... With throttle set to high, close the carb's throttle flap. You will hear the engine slow to idle but you will feel the pull from the governor spring trying to pull it open. If you let go; the governor spring will yank the throttle (very fast) to full open. The engine will over rev and then stabilize to it's preset RPM's determined by the springs and control lever orientation. This is the reason for bending the control lever in either direction. You adjust the high speed preset RPM's up or down.

When mowing or throwing snow our engine does not increase RPM's when engaging a load but it does increase throttle causing an increased flow of gas to the cylinder. This is evident by hearing the piston hit harder but not faster; to maintain the preset RPM's of the high setting of the throttle lever. Once the load is lower the governor will lower throttle input again to maintain the preset RPM's.

Hope this clears things up.

God Bless,
Dave237
 

Last edited by dave237; 09-28-05 at 02:10 AM.
  #11  
Old 09-28-05, 04:53 AM
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I totally agree with Dave237. If you still think your snowblower governor works as you describe, so be it. The governor on the 8 HP Tec on my snowblower works exactly as Dave says. Perhaps yours has a different governor on it.
Mike
 
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