Yes it could be the cam chain tensioner that's worn out. They also had worn cam problems from lack of oil getting to the rear cylinders when used too much at low revs under 3000 to 2000 for long periods so the oil didn't get to circulate properly. My sabre is starting to show engine override at high speed and acceleration through 4th /5th . And top end over 100mph. I'm hoping that it's worn clutch plates but these bikes had th common cam problem . An oil extra feeder to the heads was invented to screw on inside the oil filter thread ( external ) with two pipes that went up to the head . I think there's only two people making them in USA . But you will prob have to do the cam chain tensioners first if it is that ?
