Surging at idle and hi speed

[Gozo]

Hi,
New to this forum, just in case Gozo is an Isle in Malta, has nothing to do with Bozo.
I'm a retired Elevator tech. In N.J. always playing with machines landscaping, building walls etc.
Anyhow I got a Scag with a FH 680-V motor, blew a cylinder a few weeks ago and decided to get a new motor since the rest of it is in good shape. Installed the new motor and till today it has not ran right. This problem has got me stomped. The motor surges at idle and hi speed. Have swapped the carburetor, replaced the fuel, checked for vacuum leaks, checked fuel hoses, tested the solenoid on the carb. Filter is new comes with eng. called ECwarehouse - place of purchase and they said it could be anything, crack in manifold, carb, vacuum etc.... The other motor suddenly blew but was running perfect. This is a brand new motor nothing has changed other than the motor, what do you all think out there?
gozo

 

[impalass]

Seems like a mixture problem or maybe the governor is sticking.

 

[Gozo]

Seems like a mixture problem or maybe the governor is sticking.

Thanks for the input,
The gov. arm Is constantly moving up and down with the erratic idle, as far as the mixtures is concerened there is no adjustment screws as far as I know, I did swap the carburator and had the same result, so I do not think its carb. related. It is possible that this is a gov. problem. when I swapped the carb. I did not remove the carb. control pannel.
Moving the control pannel up or down will effect the engine speed, but not the surging problem.