After nearly a year of silence I can come along with some mods on the bike.
It now has a CB 550/650 Hybrid Engine with primary chain tensioner, CB 750 K Carbs and a (selfmade) ported head.
Let me show some photos of the build.
First I got a CB 650 engine and had it glassbeadblasted to get rid of all the old dirt and oil.
To have an overview of all the differences between the two engines, I compared the necessary parts. If someone is interested in modding his/her engine, these photos may help to get an idea of the changing dimensions (as also stated in paulages engine-mod report).
Bore-size is (nearly) the same
CB 650 Cylinder is slightly higher
Cooling fins of CB 650 are wider
CB 650 head has casted intake manifolds, which are also shorter
and not so angled as the CB 550 ones
Studs have the same position
All the parts blasted
Stock CB 650 intake ports, blasted
You can clearly see the "football", the not really smooth transition from the valve seat to the cylinders material and the thick material around the valve guides.
Exhaust side ports
After some minor unshrouding work and a little bit of material removed
After the final treatment with more material removed and smooth surface (I forgot to take pics, so here are only pics with the carbs installed, upside down, just checking the fit)
That's my first selfmade porting job, so please be merciful :-D
After reassembling the engine on a CB 550 bottom, I put it into my bike. More or less I did it like paulages did it before with the difference, that I did not make a bigger bore for the ignition's advancer but turned a pin myself from hardened material which fits into the CB 650 crank's bore of 3mm (CB 550 4mm).
The carbs were cleaned in my ultrasonic bath and provided with a new leverage for the choke, since the play in the leverage system was too bad.
I also ordered 4 carb repair kits from Japan for less than 40 dollars and had superior results.
The tank on the bike is one from my spare parts collection since the original one needs a little bit of welding because the carbs hit the petcock.
So here is the engine installed
and tuned, as you can hear and see in the following video /Thanks to crappy smartphone camera...(Thumbnail is grey but video is working!):
Cafe Racer Cb 550 650 Hybrid EngineAnd the final result from last week:
It has much more power compared to the stock setup! There is no noise from the primary chain anymore. Still looking for a good, tuneable electronic ignition to swap it against the stock one and a customized camshaft for a reasonable price. After these swaps this chapter can be closed!