1. The shimming of the five speed OSSA engine is not as critical nor complicated as previous models. It does require a slight bit of patience, but you will be rewarded with the knowledge that your efforts will result in a positive, smooth shifting gearbox.
Shimming And Gear Engagement
2. Assemble the gears on the mainshaft in their proper order. If you have replaced any gears on it, or the shaft itself, be sure the lock rings are seated properly.
3. Assemble the gears on the layshaft, being sure that they are in the right order and that the lock rings are secure. The extreme lefthand gear on the layshaft is the layshaft 1st idling gear. It rides on a caged needle bearing. When installing it on the shaft, you must first install the flat spacer washer which is approximately .040" or 1 mm thick. Then install the needle bearing and put the gear on last, over the bearing (Fig. 51).
NOTE: There are three similar needle bearings in the gearbox (Fig. 52). Two of them measure slightly less than 10 mm in width. These two are used between the mainshaft and the 5th driven gear. The third one measures 13 mm wide and is the correct one for the layshaft 1st gear. Do not confuse these bearings, as the installation of a wrong one could result in failure of that bearing.
4. With the exception of the previously mentioned .040" spacer washer inboard of 1st gear on the layshaft, and a 1 mm or .040" thick washer on either end of the kickstarter shaft, there are no other thick washers on the ends of any other shafts in the OSSA gearbox.