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Photo shows a 50cc piston (left) and a 70cc piston (right) for size comparison. In the background is a freshly bored 50cc cylinder. The 50cc and 70cc piston both use a wrist pin that is the same diameter, however the 70cc pin is both longer and has a thicker wall. |
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A close up of a 50cc piston. See the faint "IN" cast into the upper valve relief, this stands for INTAKE and means that during installation you should make sure that this side of the piston faces the intake valve. Exhaust valve relief is also much smaller than the intake relief. Piston uses the typical three ring setup. This is a photo of an actual Honda brand piston as opposed to an aftermarket item. |
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Side by side view of a late model (2000) Honda
XR70R piston and a SL70 honda piston. Totally different as you can see. XR piston is much
lighter, has a much shorter deck height, lower dome etc. Since compression on an XR is
about the same as on an SL I assume the combustion chamber on the XR is smaller. Overall,
the flatter the dome the better the combustion, assuming the same compression ratio.
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