12 motor grader clutch issue's

thanks all for the info on my 12motor grader, we have managed to get everything working amazingly. To think they were going to scrape it.
The last problem we have is the clutch will not disengage. we have tried running it with clutch pedal depressed and power on then power off, rocking it in forward and reverse with no results.
Clutch pedal has tension and seems to push fine on throw out bearing and forks.
Any sugestions on this would be great before we decide we have to pull the motor.

I filled the clutch housing on my 112 with diesel fuel and ran it. It took a bit of soaking and running, but it did loosen up.