Well the spring is trying to pull it to full throttle, and the governor is trying to close the throttle. At a particular RPM and a particular spring tension, they are in balance. So, if it won't maintain close to rpm with load increase, most likley that relationship is not functioning properly.
Under load, can you manually increase the throttle to maintain RPM? If it can't, then there is a fuel or perhaps a timing issue. If you can manually maintain RPM under load, the injector pump is capable of delivering the required fuel, so it is back to a governor or linkage issue. One usual problem area is the little yolk/fork assembly at the top of the linkage where the linkage attaches to the injector pump rack/throttle.
Sir ,
Thanks For The Explanation .Yes under load i can change the screw that either looses or tightens the governer external system and get back to high rpm .i took off the injector and the fuel pump today and took it to mico authorised service center and got it done .Refitting it just reduced the engine noise quite and but but the governer issue still is there .my linkage assembly moves freely ,Whats Wrong Guys
