1971 Tecumseh H25 Governor Adjustment Questions

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455hota

New Member
#1
#1
I have a thread started in the mini bike forum titled “ 71 Muskin Cat 2501 Project”.
I am posting this thread here since it is Tecumseh engine specifically.
My H25 on the Muskin Cat is original to the bike. Here are some pics:
The first and second pics shows the governor arm-and how it is connected to the governor shaft coming out of the engine via the special triangular bracket. I had to replace the spring that goes from the governor arm to the throttle cable linkage, as it was all stretched out of shape. The carb is not the original one but it is a tecumseh replacement one. I had to straighten the rod from the governor arm to the carb as well.
The third pic shows the throttle cable bracket setup which i believe to be original.
The 4th pic shows the governor shaft bracket ( without the Governor arm). It is rotated in the full clockwise direction.
The 5th pic shows the same governor shaft rotated to the full counter clockwise direction.
With out the governor arm attached the governor shaft does not bind and can travel fully cw and ccw.
The 6th pic show me holding the governor arm in position while the shaft is at the CW position.
The 7th pic shows the governor arm hits the engine and prevents the governor shaft from achieving the full CCW position.
The 8th pic shows the Governor shaft bracket again. I assume this interference is not correct, and i am thinking the governor shaft bracket could be loosened up and slid forward and then re secured to the shaft, providing the necessary cleance so the governor arm can achieve the full CCW rotation.
Am i on the right track here with my investigation and theory?
Also there appears to be no rotational adjustment on the governor shaft and the triangular bracket. Is this correct? It seems to me it is “clocked “ in position to the shaft, but is can be moved in and out on the shaft a small amount.
Thanks in advance for comments or thoughts... Steve
 

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markus

markus

Well-Known Member
#2
#2
That shaft that goes into the engine is bent at a 45Degree and about an inch long inside the block, the more you rotate it CCW the closer it gets to the camshaft and main rotating parts.....and BLAMO!!! The full stop it makes in your CCW pic the shaft is against the cam inside the engine. The interference between the arm and block when assembled is there for that reason, in your first pic, you have it to far CCW even for "cheating" the gov so you can override it, It will not want to operate the the levers springs as smoothly and may cause erratic behavior or not want to return to idle. It only moves a few degrees at the rotating/pivot point of that shaft when its in operation.

to properly set it (this fully assembled) loosen the arm on the pivot (the triangle) so it can move but not floppy, rotate the pivot CW till it stops (it is stopping against the gov gear/flyweight assy inside the engine) and hold it there, then take the arm that is loosened and push on the top and get WOT on the carb and tighten the screw back up. That sets your gov at full operation. From there you can make very tiny adjustments CCW to that pivot to achieve where you want the gov to keep the throttle at unloaded WOT. If you are going to use a tach to set it, Tecumseh authorized technicians to set RV engines (Recreational kart/mini bike specific made engines) at 4000 rpm +/- 150

If your wanting to cheat and manipulate is so its totally out of the equation, (not recommended if your putting you kid on it or a very small lightweight person, or if you cannot stop your now adult full size self from going full twist on the throttle and keeping it there on the open road :D) you want to adjust it out CCW just so its out of range/barely making contact internally with the Flyweight/gear that inside when at WOT. That can only be achieved Running/testing (don't hold it WOT while running to adjust though! You can make those adjustments at idle though on the stand, at least I can). You want the parts to still be as close together inside as possible because if something was to go south inside the engine with the Gear assembly, your pivot/arm will still be there to prevent it from coming off the shaft inside...and it keep your pivot shaft safely away from the moving internal parts while still keeping the pivot point of the arm in a range where it will work the carb and throttle correctly.
 
markus

markus

Well-Known Member
#3
#3
I just finished assembling a short block I rebuilt for an H25 this afternoon. This may give you a better idea of what’s inside and to go along with what I said above about setting it…….

These are the workings, note the shaft wear that is visible. It and the block wear over time so I have been making and installing inserts when needed for quite few years now on my rebuilds that are worn.
IMG_4470.jpeg

This one needed it IMG_4468.jpeg IMG_4469.jpeg

Good luck with it, I like the H25/30’s they have more guts than people think. This one is coming out nice had to go.010 over to correct the wear on cylinder and of course a standard valve seat recut and refacing of the valves to shrink seats back down to specs. That along with a few other things I do to optimize Tecumseh’s “good enough” build style, this should be a pretty strong little motor.


IMG_4471.jpeg
 
4

455hota

New Member
#4
#4
Marcus,
I greatly appreciate your detailed explanation to my rather long winded post.
sorry if I confused you with my theory/idea. I just want to set my governor correctly as it was when this engine was new. I do not wish to “cheat” the carb/throttle/governor system. I want it to run as it was designed to do.
With that being said i will follow your instructions and set the governor correctly. I think my carb is my main issue. It seems to point to a fuel issue. I have a line on a correct carb, so hopefully that will help get it running correctly. I want to make it run properly, then take everything apart for the detailed restoration. Maybe then i will send you the engine. Do you have a contact number to discuss your engine work in detail? Thanks…
 
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