Where are you located? If you start messing with the rack, please be careful. A 1/16 of an inch makes a BIG difference. Always reseat your brushes afterward, because you have changes the bevel seat.
When these machines AND engines are running to factory specs they are right on. Start checking your idle and linkage settings. Check your governor settings ( large bolt should be 50/50. screw should be against prseeure arm about 1/4") Once that is set where it should be, go to my website and read about setting your linkage. Or here is the link to Lincoln Electrics manual for it :
http://content.lincolnelectric.com/pdfs/products/navigator/OBSO_IMS/IM277.pdfYou can see a good pic of the governor here also. It is set as I described. The arm on the governor needs to break over, so do not tightened so it won't.
The easiest way to check and set your OCV's and RPM is to plug a volt/ohm meter into the receptacle on the front panel. When set properly at high idle you will read 120, and low idle you will read 87.