I did some work on the project! To make the Derbi cylinder fit I had to change the stud bolt pattern of the engine. For the Derbi cylinder to fit it had to be 56×56 mm. Originally the pattern is 54x54mm, so it is only a small difference butt it had to be done.

First I did bore the original M7 stub bolt holes to 8,5mm, so that I could cut M10 threat in them.  after that I made some aluminum threatened studs to screw in these holes. For the fixation of the bolts I used Loctite 3450, this way I am sure the won’t come loose. After this I had to let the epoxy harden before I could start milling.  When the loctite was hard enough I placed the engine in the milling  machine. before I could mill anything I had to make sure that the facing was exactly levelled. Now I could start milling. I began with searching the center of the bore, this was my zero point. From there I started bij using a flathead mill to cut of little as possible layer of the engine. The aluminium studs are now nicely levelled with casing.

The next step is to bore the new holes for the cylinder studs bolts at the exact location. The mill I use has a digital measuring system, so that makes the job easier and accurate. The holes have the same depth as the original ones, and have the same M7 threat. Only difference now is that they are further apart. The last step in this progress is cutting the new threat, after that we’re al done!

Next step for the engine would be designing an adapter to place the engine at the right height and reducing the bore. Next time more about that!

[Album niet gevonden]It has been a while since my last update. In the meantime I have done lots of things which I will show you step by step. First of all, I’ve been working  a lot on the engine. As shown earlier on I’m using a 80cc zundapp casing also known as the engine type “314”. This is a perfect casing for my project. However I have to do some work to let it fit a 50 cc derbi cylinder which I will be using. The reason I use this cylinder is because it is a very common cylinder, and I know there is a lot of potential hidden in these cylinders. Up to 24 Hp is already achieved with these cylinders.

Right now i’ve designed a very clever system to make the bore in the crank casing smaller and bringing the cylinder to the right height. Therefore I’ve drawn the complete casing in Solidworks, this way I can try some modifications without ruining the real casings. I’m a big fan of 3D printing, and the opportunities it gives you with prototyping. I would love to print some 3D parts, to fit them on the real engine, but unfortunately I do not have the resources  to do that. Maybe in the future I will! for know, let’s drop some specifications of the engine after the modifications:

Brand: Zundapp
Type: 314
Displacement: 49,89 ccm
Engine type: Single cylinder, two-stroke
Bore x stroke: 39,9 x39,9 mm
Cooling system: Liquid
Inlet system: Rotary inlet
Gearbox: 5-speed
transmission type,
Final drive: Chain

A while ago I tried fitting my bodywork. I think it looks great on the bike! Of course there are some points of improvement.  The rear needs to come down a little bit, the seat is to high know, and there is to much  space between the seat and the rear wheel. I’m also not happy with the fuel tank yet, the tank is to wide. lots of work to do!

The engine casings for this project have been sandblasted and look brand new know. The next step is to modify the original 80cc Zündapp engine cases to fit the 50cc cylinders witch I will be using for racing. I also have to make space for the reed valve inlet. Because this are originally piston steered casing, I have to change this. It’s nice I can design the inlet myself know, because the angle of inlet determines a lot of the power the engine is going to deliver.

The new self build aluminium sub frame is ready and is looking great!

This is the start of a new adventure in my life. I am building a 50cc race bike. with this bike I will participate in the Free Tech 50cc Cup.

Al progress on the bike will be shown here on my blog.