Originally Posted by FLDan

Ok, so the throttle end points and linkage allow for the throttle to open up all the way. Couple other things to check off. What fuel to oil ratio are you using?

Do you also get excessive smoke and sputtering when you apply throttle? This would definitely indicate too rich or possibly a clogged or overly oiled air filter.

If everything else checks out then I agree, definitely check the clutch...