Moving dolls head gearbox?

Hello Nicholas.

The adjusting bolt should be captive in the retaining plate that is bolted to the gearbox mounting bracket on the frame. This should then allow the adjusting bolt to be turned clockwise to draw the gearbox backwards and turned anticlockwise to push the gearbox forwards. Wear in the parts, particularly the threads,  over the years can cause a lot of slack in the system. It may be necessary to replace some of the parts if the adjuster is not working correctly.

Hope this helps, Nick  

... that as soon as you ride the bike, the extra force in the rear chain will pull the gearbox back taking up any clearance. People are often surprised that they've adjusted the primary perfectly but when they check it a couple of hundred miles later it's bar-taut.

To avoid this, always draw the box back till the primary is tight then use the adjuster to push it forward to achieve the correct slack - I like to run mine at the slack end of the recommendation. Then do up the locknut and pivot bolts, finally adjusting the rear chain.

As Ian Soady stated, tighten first then slacken by moving the box forward. my ES 2 would tighten the chain after a 50 mile ride until I was advised to do as stated above.