50 HT25 - TRENCHING OPERATION 12. Move throttle to idle and let machine idle for three minutes to cool engine. 8. When trench is complete, move track controls to neutral. 10. Raise boom. As boom clears top of trench, move digging chain control to neutral. 5. Slowly lower digging boom to desired trench depth. 7. Push track controls forward to trenching speed. 11. Drive forward, lower backfill blade and boom. 4. Increase engine speed to full throttle. 13. Turn ignition switch to stop position. 9. Move throttle to half open. p 6. Raise backfill blade.