To start with.....Here is the complete parts list for your engine.
Part of the problem could be that the governor gear..(item number 82 & 83 in the picture on this list)
These governor gears a known to break or melt inside the engine. To get to these you will have to remove the base plate of the engine. Be careful so that parts do not fly out of the engine when you take the base plat off.
Also the problem could be that the governor arm may not be adjusted correctly.
Here is a COMPLETE service manual for your engine. This should give you some more information and ideas.
The manual should help you find out if you have the linkage hooked up correctly as well. It also will show you how to adjust the governor. IT also can help you replace the governor gear just in case that happens to be the problem. Make sure that you try EVERYTHING ELSE before you tear down the engine to check the governor gear.
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