Throttle Linkage Help Techy

[McGrew 461]

I have a problem with the throttle linkage on my Techy powered Raider 10.  The throttle is very difficult to pull when trying to increase the engine speed.  This tractor was repowered years ago with a 14 HP Techy from a Bolens tractor.  The engine is an HH140, and is OHV.  When I got the tractor, it had a non original, aftermarket lever type throttle mechanism that was very stiff as well.  I replaced the throttle cable with the original pull type.  To make the cable work, I had to make my own brackets to mount it to the engine.  The cable has no sharp kinks or bends and works smooth until hooked to the linkage.  I looked at the manuals on this engine, and believe all the connections are correct.  The throttle cable pulls against the spring in the photo below.  If I disconnect the spring, the cable works smooth as silk.   I know I need the spring for the governor to work, but how critical is the spring tension?  Would a lighter spring still work?  Any thoughts greatly appreciated!  Danny

 

 

[ZXT 2,401]

If all is adjusted correctly, I don't think you should be pulling against any spring tension. It should pull on the spring and open/close the butterfly, but not have much tension unless the governor is attempting to override the throttle and shut it down. 

 

That is assuming it's anything like a Kohler, but a governor is a governor.. Didn't have any issue like that with my HH120.

[McGrew 461]

ZXT, you may be correct, but i am not sure what adjustments will change the spring tension.  When I throttle up, it pulls up on the linkage which is attached to the governor only by the spring.  The link between the governor and the throttle blade in the carb is seen better in this picture.  Danny

[ZXT 2,401]

8 hours ago, McGrew said:

ZXT, you may be correct, but i am not sure what adjustments will change the spring tension.  When I throttle up, it pulls up on the linkage which is attached to the governor only by the spring.  The link between the governor and the throttle blade in the carb is seen better in this picture.  Danny

I understand that it's connected only by the spring, but the governor and throttle butterfly shouldn't put up enough resistance to pull tension on the spring. In other words, when the governor isn't doing anything, that spring should effectively work like a solid piece of linkage.

 

Does the governor move freely without the spring attached?

[gwest_ca-(File Mod) 11,492]

The throttle cable and spring both attach to the pivoting L-bracket.

What is the distance from the throttle cable hole to the L-bracket pivot point and the distance from the spring hole to the L-bracket pivot point.

They look to be close to the same distance from the pivot point.

If you brought the throttle cable in horizontally from the left side and attached it to the top hole in the L-bracket would it give the throttle cable more mechanical advantage?

 

Garry

[ZXT 2,401]

Another thing that might get you more leverage would be to move the spring to the top hole of the L bracket. You'd have to adjust the throttle cable and the spring wouldn't be sitting perfectly horizontal, but it might help.

[McGrew 461]

ZXT and Garry,  The “L: shaped pivoting bracket arms are equal length, or very close.  Bringing the cable in from the side would not give me any more leverage.  I did consider extending the horizontal leg of the bracket, but ZXT raises an interesting question...  He questioned whether the governor arm pivots freely...  I don’t think it does, but will check it.   Should it pivot freely?  I think this Techy uses  centrifugal weights as the governor.  I have not looked at the schematics on this engine recently, but many of the centrifugal governors I have seen are spring loaded.  I will check back in as soon as I confirm if the governor shaft rotates freely.  Thank you for all the ideas! Danny

[ZXT 2,401]

One thing you might run into extending the horizontal leg.. If you extend it too much, you run the risk of running out of stroke on the throttle cable

 

The governor on my HH120 pivots freely. Yours could have a different setup internally, but I don't see why it would behave any differently at the lever.

IMG_3582.MOV

Edited June 8, 2019 by ZXT

[wallfish 18,142]

The governor lever should pivot freely with ease and you can verify that without the engine running. If it's binding then it will not operate correctly. Same for L bracket. Make sure that clamp holding the conduit isn't crushing it a little restricting movement of the wire

Whenever the engine is running, the governor is always active and trying to push the carb butterfly closed. That goes for anything from idle to high speed. The spring is necessary to allow the governor to operate correctly and adjust rpm as conditions change. The higher the RPM, the harder the governor arm will push to close the butterfly.

You can try moving the spring closer to the pivot point on the L bracket which will give more mechanical advantage.  

[ZXT 2,401]

20 minutes ago, wallfish said:

The governor lever should pivot freely with ease and you can verify that without the engine running. If it's binding then it will not operate correctly. Same for L bracket. Make sure that clamp holding the conduit isn't crushing it a little restricting movement of the wire

Whenever the engine is running, the governor is always active and trying to push the carb butterfly closed. That goes for anything from idle to high speed. The spring is necessary to allow the governor to operate correctly and adjust rpm as conditions change. The higher the RPM, the harder the governor arm will push to close the butterfly.

You can try moving the spring closer to the pivot point on the L bracket which will give more mechanical advantage.  

Maybe my mind is playing tricks on me, (which is a definite posibilty, I don't know everything), but wouldn't that decrease the mechanical advantage? I suggested the exact oppposite - moving the spring to the extreme outboard part of the bracket. 

[wallfish 18,142]

1 hour ago, ZXT said:

Maybe my mind is playing tricks on me, (which is a definite posibilty, I don't know everything), but wouldn't that decrease the mechanical advantage? I suggested the exact oppposite - moving the spring to the extreme outboard part of the bracket. 

Nope. The leverage to the spring is gained by moving it closer to the pivot because the throttle cable is pulling far out on the end, therefore the mechanical advantage (leverage) is increased. Moving the spring up to the farthest end will decrease mechanical advantage because the leverage would decrease.

 

Edited June 8, 2019 by wallfish

[McGrew 461]

Guys,  Thanks again for all the help!  I checked the governor shaft, and it pivots freely.  The cable clamp does not keep the cable from sliding smoothly, as disconnecting the spring makes it slide like butter...  @Wallfish is correct about moving the spring downward to decrease the spring's leverage.  Wallfish, I really appreciate you explaining how the governor functions, as I have had a hard time wrapping my head around it.  But I have a question.  If the governor is constantly trying to close the throttle plate (butterfly) in the carburator, what keeps it open?  The engineer in me has to understand how it works...   The only force I see opposing the governor is the airflow through the carb, but have a hard time believing the air flow on that little butterfly has enough force to overcome the spring tension.  What am I missing?   I found this in the manual on the Techy engines, and will give it a try, although I do not see those adjustments having any effect on the amount of force it takes to move the throttle.  Thanks again!  Danny

 

 

[wallfish 18,142]

32 minutes ago, McGrew said:

If the governor is constantly trying to close the throttle plate (butterfly) in the carburator, what keeps it open?

The spring tension created by the throttle cable keeps it open.

The harder it pulls on the spring, the more it opens the butterfly. The more open the butterfly, the higher the rpm. The higher the rpm, the harder that governor arm pushes to close it. The governor does exactly what it's named, it governs the rpm to stay steady under different load conditions. This is why you will notice only a very short rpm change as the engine goes from no load to heavy load like engaging the mower deck.

 

[gwest_ca-(File Mod) 11,492]

All the parts look factory made to me. That leads me to believe something else is wrong.

What happens if the initial governor shaft to governor lever setting is not correct?

That adjustment is covered on the bottom left of the page McGrew posted but I don't understand what they are doing because I have never seen these parts. They are different than what we see on Kohlers.

If the initial governor setting is not correct I think I can see how the governor believes the engine is at high rpm when it is actually at idle so maximum governor force is preventing an increase in rpm by the throttle.

 

Garry

[ZXT 2,401]

3 hours ago, gwest_ca said:

All the parts look factory made to me. That leads me to believe something else is wrong.

What happens if the initial governor shaft to governor lever setting is not correct?

That adjustment is covered on the bottom left of the page McGrew posted but I don't understand what they are doing because I have never seen these parts. They are different than what we see on Kohlers.

If the initial governor setting is not correct I think I can see how the governor believes the engine is at high rpm when it is actually at idle so maximum governor force is preventing an increase in rpm by the throttle.

 

Garry

That's what I was thinking, but wouldn't he only have the issue when the engine is running? From the way he's talking it seems like its the same whether it's running or not.

[McGrew 461]

Garry and ZXT, you are correct, the throttle cable is very hard to move regardless of whether the engine is running or not.  I think I should mention that the governor seems to work fine.  I pulled a 500+ pound spike aerator up and down my hilly yard several weeks ago with little or no change in RPM.  I think the clue to what is causing the problem is that removing the spring makes everything work smoothly.  I agree that all the linkages on the engine are factory, bu have no idea what type of throttle cables Bolens (donor tractor for this engine) used.  Maybe it had some additional mechanical advantage?  Maybe a long lever type throttle?  I am going to try moving the spring and see what happens.  I want easier throttle control, but still want the governor to work.  In other words, I want my cake and eat it too!  Danny

[wallfish 18,142]

36 minutes ago, McGrew said:

the throttle cable is very hard to move regardless of whether the engine is running or not

Moving the spring will NOT help. The tension on the spring from the gov is only there when the engine is running. I was under the impression EVERYTHING moved freely, All linkage and throttle cable but resistance was when the engine is running.

Try disconnecting the Z bend throttle wire from the gov bracket. Re-tighten everything back as it was and check the resistance in the throttle cable again. 

Are you sure that conduit isn't being crushed by the clamp point on the engine? Or there is a bend in the conduit which is too sharp?

All of the gov and throttle linkage should be moving with ease.

It's impossible to have completely free moving linkages without any binding at all and have a completely free moving cable without much resistance and then have restrictive resistance when they are connected only by a Z bend in the wire.

If all of the linkage is moving free and easily with the engine not running, my guess is the cable is binding. The idea is to try and isolate the issue to either the cable or the linkage.

[McGrew 461]

Wallfish,  The cable is not binding.  There are no kinks or sharp bends.  The proof the cable slides smoothly is when the spring is disconnected.  With the spring disconnected, I get full stroke on the throttle cable with little or no resistance.  You did hit on something though... You said the spring only applies tension when the engine is running.  With the engine not running, if I pull the throttle to anything more than idle speed, the spring starts to stretch.  This is the reason the throttle cable is hard to pull.  I guess it is possible the governor linkage is so far out of adjustment that is where the problem is?   I have not changed any of those adjustments since getting the tractor.  The only modification I made was changing the aftermarket lever throttle cable back to the original pull style.  Danny

[wallfish 18,142]

So it's definitely in the linkage and or gov setting. First thing to do is take that manual and follow the instructions for setting the governor properly. Your teccy could be different but all of the smaller engines I have, the linkage moves freely from idle position to full throttle when the engine isn't running. After setting the gov properly you can adjust that spring to your liking. By creating more mechanical advantage you should feel a difference in the resistance.The trade off is you have to move the throttle knob farther the closer to the pivot point that spring goes. The plus to that is you get better setting control for the RPM

[McGrew 461]

Thanks Wallfish.  I will do just that.  As soon as the wife allows me the time...    One thing I do need to correct:  I said the spring starts to stretch at anything above the idle.  Not correct...  I can pull the throttle to almost mid throttle before the spring starts to stretch. Until that point, it acts as a solid link.  I will make the adjustments and report back.  The only problem is we are in the middle a a monsoon here in the Deep South, and not expecting any sunshine until Thursday...  Danny

[McGrew 461]

Guys, I wanted to post a follow up.  Wish I could report something good, but that is not the case.   I  adjusted the governor according to the sheet I attached above.  All the pivot points move without binding, and the cable is smooth as silk, but the throttle is still so stiff I actually fear pulling the knob off the shaft...  It works with normal force until the spring starts applying tension.  I am beginning to wonder if the spring was changed out along the line, and someone put in a Godzilla spring?  If I remove the spring, the throttle cable will go through the full range of motion with very little force.  And the governor works well.  I pulled a 500 lb. spike aerator in second gear high range  up some steep hills this weekend, and the engine never lost any rpm...   Unless someone has another idea, I am going to try a weaker spring and see what happens...  Danny

[gwest_ca-(File Mod) 11,492]

I would think the spring tension is very critical to governor operation. I recall reading that the spring must not be forced when installing it because it would alter it's tension. The instructions were to remove one of the levers so the spring could be easily hooked on so have always done that and never had a problem.

Looked at a couple and looks like at least some of the springs are still available

https://www.partstree.com/parts/search/models/?searchTerm=oh140

 

Garry

[McGrew 461]

Garry,  I agree the spring tension is critical to the governor operation.  I tinkered with it a little this evening, and rather than changing the spring, I changed the location of the spring on the governor shaft lever.  This lever has six different holes all within an area about a half inch square.   The tech manual on this Techy says the spring should be in the bottom middle hole.  I moved it to the hole just to the right of that hole, and was surprised how much difference it made in the adjustments.  This hole is only 1/8” from the hole the manual says to use, but had to move the throttle cable almost a half inch to make it work.  The throttle seems to move more freely.  I got it all buttoned up, but did not get a chance to test it.  Hopefully tomorrow...  Thanks for all the advice!  Danny

[McGrew 461]

Okay guys, I have an update.  I have had a lot going in the last few months, and did not have a chance to work on the linkage.   I finally got around to making a new bracket to extend the length of the arm where the throttle cable attaches.   I took some crude measurements, and found I only using  about an inch of travel on the throttle cable to go from idle to wide open.  The throttle cable is supposed to have 2 inches of travel, so that is what I shot for.   I added an extension  bar to the original pivot that lengthened the point of attachment from 2.75" to 4.25".  The cable now has almost 2" of stroke, and is very easy to operate.   I did have to modify the cable bracket as well, and mount it on an angle.   The original setup looked cleaner, but I am a function over form kinda guy.   I am just happy i can adjust the engine speed now without having to pull hard enough to pull the knob off the shaft!  In the picture below, the screw on the left is in the location where to cable used to attach.  Danny