recent developments

The C110 cases are blasted, cylinder and head are still to be done.

But I needed the cases clean so I could look if an SS50 5speed gearbox would fit in there. Someone once told me it would fit with a minor adjustment to the shift drum, but I think he never realy looked into it closely.
The 5th gear would interfere with the wall that seperates the gearbox from the ignition, not impossible, but a lot of work.

But it gets harder still, the total gearbox of an SS50 is wider by about 5mm....
this would mean major surgery to fit a 5speed gearbox.

This project is off the table (for now..), the C110 will get a normal 4speed cluster.

This just in:
My titanium valve spring retainers for the RSC90 arrived last week, so the C110 engine will go to the back of the workbench for a while, to build up the 90 motor completely, everything is ready, just needed these retainers to finish the head.
Now I can look at valve spring compression, if I need racing springs or if I can use original and so on.

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.

rear brake

I finally decided how to attach the rear brake cable.
As the footpegs are made for a brakecable and the original S90 brakeplate is meant for a brakerod, there was a problem.
I didn't want to weld anything to the brakeplate, but I couldn't decide on what it should be, untill last weekend, when I made this bracket.
I know similar brackets exist from aftermarket suppliers, and yamaha used something like this on their 125 production racer back in the days.



It is bolted with the brakestay and has a lip that falls against the edge of the brakeplate, very simple but effective.

CR110 replica forks

I recieved 2 sets of CR110 front-fork-spring-support-rings (anyone for scrabble?) that I bought on ebay. One set will be for the RSC90 but the other is for an actually abandonned project. A Honda CR110 replica.
It was the plan to build frames and really change mine and my dad's CB50 racers into CR110 replicas, but the 50cc class has become too fast with modern 2stroke tuning, so I am abandonning the class altogether and also the CR110 project.
All the parts I allready had will be used on other bikes probably, or maybe sold.
The front forks were allready made for this project, it only needed these rings, so when I got the chance, I bought them.
It supports the spring where it rests against the lower yoke.

I think this fork will go into my SS50 motorcycle, combined with a front fender like the one made for the RSC90 and the same type of 160mm front drum laced to a WM00(1.20) alloy rim.

Will need to make some clip-ons to mount the original CR110 levers onto....

RSC front fender, part 4

Last weekend I went on with the front fender for the S90 racer, I didn't really feel like it, but in the end I was glad I did the work.


mounted on the bike:


The weight really surprised me, and it still functions as a stabiliser because of the supports underneath the fender, just like original.

On to the next long project that has been on a rest for a while, the model for the gastank....

brakepedal

My brakepedal was still smooth on top and I wanted it to have teeth on the flat surface, like a C(Y)B72 pedal. I never made something like this before, but I think it turned out pretty nice. Milled with a 20degree cutter, set at an angle.
In hindsight I should have made bigger teeth, but I can do that when this has worn away from use.

12 Volts

The oudshoorn gets some real electrics, no fuss with a vulnerable old 6volt system, but 12 Volts out of a /6 Beemer.

And it still fits under the original front cover.

a little history

I found this picture on the web, on this Belgian blog This is the Oudshoorn BMW a long time ago.
Before I was born? as I don't remember it like this, never seen black valvecovers or those dellorto carbs.



The caravan in the background I do remember, sadly the wood rotted away, but we still have the chassis which is now a trailer for my dad's sidecar.