Honda Cub 70cc to 100cc conversion

I finally bought a Honda Wave 100 engine for my Honda C70 EX3. Here it is.

Of course I wanted a 110cc or maybe even a 125 but I settled on a 100 because it’s just really hard to find one for sale that’s either still intact and nearby. I had been waiting almost a year and drove 80km to Laguna (back and forth) to pick this one up. Most are sold in smaller pieces so the seller can make more money.

We are transferring the internals and not swapping the engines (which would have been far more easier) because I want to keep the engine number on my registration the same.

Here is my opened crankcase on top and a Sym 100 crankcase my mechanic happened to have lying around at the bottom.Here we can see the 4 gears for the Sym shoots right into the EX3 crankcase.

And vice versa.

An issue we realized is that the EX3 has a neutral indicator facility which we won’t use hence will leak oil. This needs to be taken to a machine shop so they can find a way to close it up.

The Sym crankcase does not have such a facility.

So those are the developments for Day 1. On Monday tomorrow I will take that crankcase to a machine shop to get some answers and watch the mechanic open the Wave 100 engine. My ride awaits:

3 Replies to “Honda Cub 70cc to 100cc conversion”

  1. Hi
    My names Isaac and I’ve been thinking of doing the same thing; however I can’t find anyone who has done it.
    I’ve a Honda cub that has been bored out, but I want to make a second and swap the 50cc engine for a Honda wave 100cc engine.
    Is this possible or would I need to weld and drill different holes.
    Once again thanks for the time taken to post this post.
    Many thanks

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