I am just going by my other 6hp there is a stop cast into the starter bracket...And the cam can only rotate until it hits the stop.....And there is a small gap on the throttle control lever at the back under the flywheel....But on this motor the throttle control lever hits the ring under the mag plate and there is at least 1/8 of an inch gap at the cam stop..... I can push it to the stop by hand.... But turning the throttle will not make it go completely around because of the lever making contact... Sorry for not making it clear enough... I should of mentioned the cam stop.....
OK, with that info, there has to be some problem with the curved bar that links the vertical shaft with the mag plate. Hard to think it might be bent. OR a problem with the cam/stop. Examination required.
The one in the photo is up against the stop and there is a slight gap between the control lever and the brass ring under the mag plate... The other I can here the throttle control lever striking the brass ring and the cam does not touch the stop....
