Throttle Question--What is this?

grass1950

13 years ago

Last week the throttle on my Linamar 720 aka Onan P220 stuck at full throttle. Cleaned linkages and carburator with rattle can cleaner and regained full throttle/engine speed range; except, the engine would not hold full throttle/maximum engine speed.. Per the manual, all linkages and governor spring were at factory spec positions. Adjusted governor spring to reduce sensitivity and throttle attained full engine speed range. Today I returned the governor spring to factory spec (original) position/sensitivity setting and the throttle/engine speed range continues to opperate as intended.
What has me puzzled is that there is a spring that runs parallel to the governor control linkage/rod that is not pictured in any parts or manual. The control rod actually runs through the center of this springs coils. One end of the spring is attached to the throttle plate's external control lever in a hole next to the hole for the governor control linkage/rod. The other end of the spring is attached in one of two holes (for sensitivity adjustment?) next to the hole for the governor control linkage/rod on the governor arm. If the linkage arm was not there, this spring would cause the throttle plate lever to seat against the idle control screw and bring the engine to idle.It seems to have no function but it does seem to get hung up on the rusting surface of the governor control linkage rod. What is this spring for? Is it a safety device? Could it have caused the engine to not hold full speed?
Thanks for taking the time to read this.

Linkage picture (on the right):
http://htmlimg2.scribdassets.com/137bhtq64gtsp0u/images/24-7724a6b47f.jpg

Here is a link that might be useful: {{gwi:343708}}

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Comments (5)

mownie
13 years ago
When these types of springs are found in conjunction with governor linkage, their purpose is to apply positive pressure against the levers that the rod connects together so that any wear (sloppy fit) will not cause the governor to "hunt".
I call them "anti-slack" springs.
The spring in itself should not be able to influence governor action unless it is somehow causing something to bind (as you suggested).
Any chance this might have been added by a previous owner? Or is that you?
grass1950
Original Author
13 years ago
I am not the original owner. Bsed on the appearance of the spring (ageing) and the fact that there are separate dedicated holes where it attaches (unlike your illustration, the ends of the spring do not share the same hole as the link rod), I'm pretty confident that this was not after market and was factory installed by the tractor manufacturer, if not Linimar.
I'll polish the rod to eliminate the kinking.
I'll store this info as a possible cure for the next time I come across an engine that is "hunting."
Thanks mownie.
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mownie
13 years ago
Well, that image was something I cobbled up to depict how the spring action draws the levers tightly against the linkage rod to eliminate slack.
I based it on a Briggs application but I had no photo so I sketched it out some years back for a different thread here.
But it is the same concept whether they use the same holes or dedicated holes for the spring.
By the way, the spring (in my sketch) actually DOES NOT have any relative motion to the link rod. The spring and the rod move together as a single unit.
Now, yours.............being as the spring connects at different holes, may actually have some relative motion between the rod and the spring as the linkage and levers move through their respective arcs, but i would not anticipate that to cause any profound effects as to operation.
grass1950
Original Author
13 years ago
Lol. I hope you don't think I was being a critic of your illustration. Your drawing is very much like what I have, I just pointed out the extra holes as evidence of it being OEM. The fact that the rod and spring move together as a single unit is why I questioned the spring's purpose. Now I understand.
mownie
13 years ago
Not at all. I was simply discussing the differences, and similarities.