Re: Cub Loosing Power mowing

Posted by dnoha on October 08, 2001 at 14:07:51 from (205.245.122.225):

In Reply to: Cub Loosing Power mowing posted by pkoeppel on October 08, 2001 at 10:36:47:

Could be something about the carb, know nothing about them.

Might also be the governor. Replacement of the carb would have affected its connection to the governor and whoever replaced it might not have rebalanced the governor linkages. This connection needs to be carefully balanced for the governor to affect the throttle appropriately.

When you hit tall grass, the engine will slow down under the increased load. This slows the weights spinning inside the governor, reducing the thrust they impart to the governor rockshaft. The governor spring then wins the battle with the spinning weights and turns the rockshaft to push the throttle rod to get more gas to the engine to speed it back up. This creates a little tug of war between the spring and the weights where lower RPM's favor the spring and higher RPM's favor the weights.

When properly set, this creates a balance between the spring and the weights, allowing the operator speed control lever to define that balance (in terms of engine RPM's) keeping the engine speed relatively constant under varying loads. There is a relatively narrow range of RPM's over which the spring and the weights can be balanced.

To see if this balance is out of whack, turn the tractor off and set the operator speed lever to full speed. Since the governor weights aren't spinning at all, the spring should be putting sufficient tension on the governor rockshaft to push the throttle rod wide open against the stop on the carb. If it isn't, the adjustable rod connecting the carb throttle to the governor rockshaft lever needs to be lengthened.

My manual says this rod should be set so that when the operator speed lever is at about the half advanced position (straight up, parallel with the steering support), the governor spring should just be starting to lift the governor rockshaft. (Easiest to see from the left side of the tractor, sighting along the governor rockshaft back to the governor.) When you get it all set right, you should be able to use the operator lever to control engine RPM's from slow idle up to fast idle, and the governor should be able to get you to max throttle when the engine needs the extra power.

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