You can jam the primary with a block or rag with the old five speed transmission but not with the six speed, you risk cracking the case by jamming the primary chain against it or putting too much lateral pressure on the output shaft bearing. I appreciate you think you know something but you all know fuck all, I have had the primary and transmission out in the past to replace the output shaft bearing as it was a casualty of driveline shock when the bike was in an accident before I bought it. I know what I am doing and I will do it properly.