Originally Posted by dutch1
The linkage plate that is immediately below the carburetor is retained to the two the opposing heads by two 6mm bolts. You will find that the linkage plate under the right hand bolt is slotted. With the throttle control at full throttle, loosen the two bolts and raise the linkage plate a bit to elevate the rpm. I usually do this with the engine running and a digital tach attached to a plug wire so I can get the desired rpm and lock the bolts down.
Maybe Restro will show up and post a diagram with more easily understood instructions. I am not that computer literate nor do I have access to online service manuals.
Is this located under the air filter box? Please excuse the ignorance!