HM80 throttle linkage issues

FOMOGO

FOMOGO

#1
#1
Can someone confirm if this is correct on my SB. The throttle doesn't want to close if the move the lever that the cable pulls at all. If you move the lever far enough to close the carb the spring on the arm is totally free and not returning the arm any longer. In the pic you can see that the lever is rotated so far that the spring is free on the right side by maybe a 1/4''. Its got me baffled. It is as if it is missing a spring but its all there. It will crank and run but it doesn't want to return to idle unless you pus the lever down with your finger. You can see how far the cable stop is and that is where it frees up the linkage until it will go back to idle.

Spring not making contact.

If you move it just until the slack is gone out of the spring then it is opening the carb.

Am I missing something or is something missing? I cant figure it out. It acts like it needs a return spring but I thought that was the purpose of the spring on the throttle linkage in the pictures....

Help......

Doug
 
OND

OND

#2
#2
Doug here is a pic that I borrowed .



Hope this helps .





Doug I can't see the rest of your set up....sorry . When I enlarge your pics they are super large . [MENTION=53722]FOMOGO[/MENTION]
 
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FOMOGO

FOMOGO

#4
#4
Well the whole fight is with the little bell crank piece that the throttle cable pulls. If you raise it at all. Like the cable would pull it up. The spring between it and the lower bell crank seems to be way to short and engages the governor arm which in turn open the carb. You have to pus it down further than the return spring rotates it in order for it to let the carb go back to idle.

Tell me what you guys need to see and I will take better pics. This is why I haven't put the muffler or seat back on it yet as it is all in the way. Much easier without that stuff on it.

The governor is all functioning as it should but I am thinking that little spring between the upper arm that the throttle cable attaches to and the lower arm that pulls the governor arm is to short. :shrug:

The governor arm if that helps....

 
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FOMOGO

FOMOGO

#5
#5
Here are a couple more pics. After going back out and studying it a little more I think the governor arm needs to be adjusted a little bit. There is just no return offered by the governor.

Here is a pic with the upper arm fully returned and you can see the carb is closed. The second pic is with the upper arm pulled up just enough to engage the return spring that wraps around the pivot bolt and you can see the carb is opened about half way.



Does this help?

Doug
 
2SlickNick

2SlickNick

Well-Known Member
#6
#6
Doug I have that exact same engine. I got so frustrated with the linkage I took the governor arm out. Maybe I should put it back in I don't know.

I need to replace one of the valve spring retainers...
I just can't get the damn thing running right. I even bought a new carburetor still can't keep it running right.

I have to keep that engine and make it work because it goes with my mud bug trike.

I will be following this thread.
 
Dr. Shop Teacher

Dr. Shop Teacher

#7
#7
1) The cable stop is adjusted too low. It should be at upper control. Make sure that spring is free to pull the upper lever to "neutral."
2) Yes, the governor arm can get out of whack. It operates opposite of what is intuitive. Micro adjustments (1/32th or less) make huge differences. NOTE: The actual governor does not move more than 20 degrees total duration...so any bad adjustments WILL send the bike in motion if you don't have it blocked up off the ground.
3) You do have the spring in the wrong position on the bell crank: use outer most hole. Rummage around or make a run to the hardware store and grab a few different springs of varying tension but not length to try.
4) The only images of HM80 throttles are of the "new" style (even in manual), so the H50 set up Eric is showing offer best clues. Just make sure the rod from the governor arm is located in the proper hole on the carb (trial and error).

This is the joy of Tecumsehs! Once you get it, it will all make sense---and post a how you did it as there is nothing on the site but how to bypass.
 
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OND

OND

#8
#8
I don't know what's going on this morning ...Doug's pics won't even open all the way for me this morning.....seems like Pete can see them though.
 
FOMOGO

FOMOGO

#9
#9
Dr. Shop Teacher said:
1) The cable stop is adjusted too low. It should be at upper control. Make sure that spring is free to pull the upper lever to "neutral."
2) Yes, the governor arm can get out of whack. It operates opposite of what is intuitive. Micro adjustments (1/32th or less) make huge differences. NOTE: The actual governor does not move more than 20 degrees total duration...so any bad adjustments WILL send the bike in motion if you don't have it blocked up off the ground.
3) You do have the spring in the wrong position on the bell crank: use outer most hole. Rummage around or make a run to the hardware store and grab a few different springs of varying tension but not length to try.
4) The only images of HM80 throttles are of the "new" style (even in manual), so the H50 set up Eric is showing offer best clues. Just make sure the rod from the governor arm is located in the proper hole on the carb (trial and error).

This is the joy of Tecumsehs! Once you get it, it will all make sense---and post a how you did it as there is nothing on the site but how to bypass.
Click to expand...
Pete the Governor arm was loose because the linkage from the arm to the carb was missing when I got the bike. So I assembled it with the correct parts and adjusted the governor initially per the manual. I don't think I have the governor arm far enough towards the carb as there is just not much return pressure from the governor. The other HM80 I have I looked at last night and discovered that it had a lot more push back from the governor than this one. I am going to adjust the arm again and see if it improves the return. The spring you are referring to has never been off and I have to assume that it is where Tecumseh put it when they built it. I will look at the other one and see where it is. Just my experience but if I go to the outer most hole wont that speed up the movement of the second lever? I know that we put longer pitman and idler arms on early Mustangs to increase the steering box ratio.... speed up the steering .


Doug
 
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Dr. Shop Teacher

Dr. Shop Teacher

#10
#10
^^^pic above^^^ Not sure of the age of the engine, but that sure looks like a more contemporary governor arm (I have basically the same on my 88 H60 w/new style control). The older models had a second tab attached to which the rods attached. Joe51, when I bought a control from him, showed the spring on the outside hole. Your analogy makes sense--the spring WOULD return quicker with more tension. Below is the old style H60.


Looking at the pic above, the little tab is on the upper arm: Obviously not the way an HM80 is set up. The little tab allowed for micro adjustments to the carb w/o changing the position of the longer arm on the governor.

If you disconnect all the pieces to the governor rod coming out of the block, that little rod only turns a little bit (the 20 degrees or so). So any change on the arm that comes off of that rod, will be amplified pretty dramatically because of that 3" or so length. Even so, since the travel is minimal, I don't see how this would be the root of the problem.
 
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capguncowboy

capguncowboy

Well-Known Member
#11
#11
Doug, the diagram on partstree shows a link being used from the bellcrank to the governor arm being part number 33372

https://www.partstree.com/parts/tec...-cycle-horizontal-engine/engine-parts-list-2/

A quick search took me to this part on Ebay.

Tecumseh engine 33372 governor link brand new genuine OEM | eBay

The governor rod is bent. that makes sense though. If yours was bent, it would get the bellcrank into a more elevated position and correct some of your issues.

Just my 2 cents, and maybe it is bent but it's not showing in the pictures? Figured it was worth a thought
 
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FOMOGO

FOMOGO

#12
#12
Thanks Andy! I will look at that as I do believe that mine is straight.

The number one thing I cant overcome is the governor is giving almost no return pressure to close the carb. My other HM80 has a lot more return pressure from the governor closing the carb.

I wont give up but its trying its best to whip me....

Doug
 
FOMOGO

FOMOGO

#13
#13
Okay. Its alive. Here is what I did. After Andy made the above post and I looked at the governor rod in the link he provided, I figured I had nothing to loose but a few minutes time. So I looked at my rod which had just a hint of a bend and I added to that so that it aint hinting no more. It brought the lower arm up allowing me to raise the upper arm until the return spring was just touching. I think it could even go a little further for just a little better engagement of the return spring on the upper arm. I fired it up and the governor held the carb at idle with no problems and the throttle would return to idle with no trouble. I haven't ridden it this way so I cant comment further but it responds nicely to the throttle and returns properly to idle on the stand.

I shall post further when I get to ride it some.

Doug
 
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FOMOGO

FOMOGO

#16
#16
capguncowboy said:
Awesome news Doug! Hopefully, you'll get some nice weather this weekend to ride it!
Click to expand...
I wont be riding it tomorrow that's for sure. My buddy Bruce and I are going to Commerce, Ga. for the swap meet in the morning and then by lunch time we should be passing along the back side of Greenville heading to an indoor car show in Ashville, NC..... The day will be a little long but both events are well worth the ride. Head out at 6 for Ga. and hopefully be in NC at the car show at 1. Home by 6 and its a day.....

Now Sunday I probably will be sleeping... I would rather be riding the bike if I can.
 
FOMOGO

FOMOGO

#18
#18
Dr. Shop Teacher said:
Glad you got it sorted. Take a good set of photos and post it in a new thread as "HM80-linkage set up." That'll help a lot of folks with this engine on their big bikes.
Click to expand...
I haven't ridden it yet and am not convinced that it is fully sorted yet. I think that a little more bend might be beneficial. I wont know until I ride it enough to see how it does.

Once I get to ride it some I will post the results here for everyone to see.

And you are correct that it would make a good "How to" thread. Once I have it sorted I just might do that.

I think I will go and install the old seat and go for a ride. I am afraid the rear brakes are going to be a pain.... Just have to wait and see.

Doug
 
superflea

superflea

#19
#19
Well I have the exact opposite problem. On a new HM80, I have hooked up the cable and all is well when off. The throttle opens fully with engine off. Once the engine is started, all I can get is idle speed as the governor totally overrides the cable control. While riding it I have reached and tickled the throttle on the carb and it about knocked me off the bike. I am ready to try and bypass the Gov. because I want to deliver this VT8 and a Taco 44 to my don and grandson on Sunday.

Fred
 
Divouneh

Divouneh

Active Member
#20
#20
See what I done to test my engin, the final solution (after the refurbish from all the Bronc) will be the same just more clean.
Governor is off also, direct connection from carburetor
to throttle.


Divouneh,
 
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