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Vech said that the engine looked like it had much more that the 53,000 km indicated on the odometer. The slingers were full, one of the rod bearings were shot and the inside of the engine was one of the dirtiest he had ever had the pleasure of working on. Since we needed a new rod kit and the next oversize pistons, we had an opportunity to use more ‘modern’ components. We decided to use the pistons and rods for a later model R50/2. The new pistons are the three ring design in contrast to the original five ring (three compression and two oil scraper rings) pictured below. |
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| The five ring piston must have created a lot of friction
and heat which might explain the very low maximum speed of 35 mph during
the first 1000 km break-in period specified in the owner’s manual. The major distinction between the R51/2 and the later magneto fired bikes is what you find when you remove the front cover. |
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| Instead of a cam driven magneto and a crank driven
generator as on later twins, you find the left cam used to rotate the
points and drive a rotor inside of the distributor cap. This set-up is
very much like the ignition system used on the singles. At the left hand
side of the distributor cap you can see the cable used to advance and
retard the ignition. The hex head plug below the distributor provides access to check the tension of the timing chain which wraps around the generator at the top, the two cams on the left and right, and the crank at the bottom. Since the generator drive gear is off-center, rotating the generator is the way you adjust the tension of the timing chain. Elaine says you cannot hear the timing chain make any noise when her bike is running. I hope mine ends up being as quiet. |