The gearbox is pivotally mounted on a bolt passing through the bottom of the housing, and the housing is held between the two rear engine plates. The driving load upon the rear chain always tends to pull back the gearbox and would tighten the front chain excessively if no positive means were provided to stop the gearbox "working ' back. A draw bolt is fitted behind the rear of the two top gearbox fixing bolts and passes through an "eye" bolt fixed to the engine plate (see Fig. 13). Two nuts are fitted on to the draw bolt by means of which it is possible to move the gearbox forward or backward on its mounting after the fixing bolts are loosened.

Slacken the nuts on the three bolts which hold the gearbox into the engine plates, one at the bottom and two at the top. The adjusting nuts (Fig. 13) are on the right-hand side of the machine just alongside the rear engine plate. To tighten the chain, screw the front nut forward along the draw bolt a little and then turn the rear nut forward until it is tight. Check the chain adjustment, after tightening the fixing bolts. If too tight, loosen the fixing bolts again, screw the rear adjuster nut slightly to the rear and follow it up with the front nut. Tighten fixing bolts and check the adjustment. Finally check the adjuster nuts for tightness.