C110 engine stripdown

When I bought my C110, I had a choice of two engines I could get with it for spares, from what you will see next, I think I picked the right one.

I started taking apart the spare engine today, The plan was to give it a bigger piston, some tuning work and getting it nice and clean in the blasting cabinet and repainting the cast steel parts.

When I took of the head cover, the rockers looked a little funny to me, but I thought that might just be 1960's production.
when the valvecovers were taken off you could clearly see that someone had lightened the rockers, and had even ground down the adjuster screw and bolt on the inlet side.

And when I took of the head, I was surprised by a high domed piston:

This looked very high to me, I couldn't wait to compare them to the pistons I had back home.

By now it was clear that this wasn't a standard engine, someone had done some tuning, but for what purpose?.....
The kickstart hole was blocked off with a piece of cork or rubber, so I assumed the shaft was snapped, as this happens a lot to C110 engines.

But when I opened the engine up, there was no kickstart shaft...
This engine was used for racing!!!


My C110 came from the north of holland, where they used to do grasstrack racing, could this have been used in a 50cc class, as the high domed piston and lack of headgasket would indicate a very high compression.
Also, the oil residue was very thick and my dad recognised the smell as old racing oil.
Did this engine run on methanol?

I took the piston home.
At home I had two pistons, that I thought were C110 and CY110, but now I don't know anymore.
From left to right C110,CY110,super racing piston????
or C100,C110,CY110???
If you know, please tell me.
All pistons are 40mm and marked "ART" ,as you can see, they gradually get higher.