Engine assembly is done! Honda CT70 project continues | Redline Update #90 - Hagerty Media

The small scale of the Honda Trail 70 means updates and progress happen fast. For example, Davin took a trip to the machine shop to get the precision bits cut to size and ready for assembly. Then he couldn’t help but go ahead and put it all together too.

The cylinder was the first thing to get mounted into the machines at Thirlby Automotive. A quick pass with one of the smallest boring bars in the shop brought the bore not only to properly round, but also to the size appropriate for the new piston. Final size was set with the hone to make everything just perfect. From there the attention shifted to the cylinder head.

The valve seats and corresponding valves were not in the worst shape, so the team decided to cut the valves and give a quick grind to the seats. This created fresh sealing surfaces to make sure the small valves won’t leak. It’s a simple process that requires a careful hand when dealing with parts this minute. The team at Thirlby provided that steady hand, and the finished product was soon ready to head back to the Redline Garage for final assembly.

That assembly went fast, but it was important not to miss any of the precision checks in the flurry of assembly excitement. Take the piston ring end gap, for example. The shop manual laid out the specs, and Davin got lucky that the new rings were perfectly in the middle of the range that was called for. Some oil and the cylinder slid down over the piston, followed by the cylinder head and valvetrain.

A couple of final touches and the engine was complete. It’s now ready to be slipped back into the chassis. If you want to see that, you’ll have to tune into a future Redline Update. Make sure you never miss an update by subscribing to the Hagerty YouTube channel.

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