Hello
Thanks again for the replies. I noticed a typo in my last post, where i was talking about the oil, when i said ".... the near identical KS 175" i actually meant to write "KS 125". Please forgive me, i was at work and in a bit of a hurry.
Regarding the KS 125/KS 175, they are indeed using the same crank case and indeed the KS 175/Fury are literally a bored-up KS 125. Same stroke, but different timing (the KS 125 has the exact same power of 17 horse powers but has a much more narrow power band, you ride a KS 125 much more like a sports bike, i.e. always in high rpm's as there is not much torque, however the KS 175, while making 17 horses power as well, is an entirely different beats - in Germany that particular engine is nicknamed "Buffalo" for good reason, as mentioned "torque like a tractor".
So in short, yes, it is entirely possible to plant a KS 175 cylinder onto a KS 125 block, but you will need to change the crank shaft and the (Stehbolzen, what is it in English..?) long bolts that go from the crank case all the way through the cylinder to old the head with 4 nuts. However maybe YOU don't need to do that as the Fury's cylinder is air cooled like the KS 125's, while the German KS 175 is exclusively water cooled.
As to "boring up a 125", this unfortunately is not that easy. As Zundapp has never used cast-iron or similar cylinder liners, instead they used hard-chroming of the aluminium bore, which makes it difficult and extremely expensive to hone any Zundapp cylinder. However you could use a regular KS 125 cylinder and put it onto a Fury's block (again crank shaft swap required!) as you will have the same power - if you like to ride sporty it is an option. The carb is the same one as well, a 26mm Mikuni. However your Fury will then be "degraded" to be a 125. so don't tell anyone.
@silver_shadow
Sadly i didn't know your user name here, otherwise i could have entered it into the "referrer" bit while signing up, but many many thankls for bringing me here, i really appreciate it and truly hope i can be of help here.
@siddharta
"Kardan" (not "Kardon") means "drive shaft". Kardan models don't have a chain but a, well, drive shaft to drive the rear wheel. And not all the "KS" models feature a drive shaft - as the "K" can also stand for "Kastenrahmen", those are where the frame is not made from welded tubing but pressed sheet metal. This naming proved popular so later models retained "KS" even though they had neither a drive shaft nor a pressed frame, basically, all of Zundapp's higher-end bikes were named "KS" such as the KS 50, KS 80, KS 125, KS 175 and the planned (but never built in series) KS 350.
If you do a little research on Zundapp you will find all sorts of model types, all of which originate in German words, with one notable exception, coincidentally one you know locally - the Explorer. It's German name "CS 50" dates a looooong time back, to Zundapp's very first small engine - the "Combimot" that could be attached to bicycles. Zundapp's first moped, based on that engine, was then called "Combinette" and an advanced version of same was then called "Sport Combinette". S-C-50 so to speak.
Over the years there were many many different "Sport Combinette" models, and in the late 60's this was finally modernized - the C(ombinette) 50 Sport was born. C-50-S so to speak.
This was now the lower of Zundapp's 50cc mopeds with it's three speed transmission - at the same the GTS was born, a four-speed and otherwise near identical. Going through the 70's the GTS became more modern as did the C50 Sport, but in the 80's then the big change came - the "open 50cc class" was abiolished in favour of the new 80cc class, and Zundapp re-used the production lnes for the KS 50 (now no longer produced) to make the same as a moped, reduced to 3 HP (from 6.25), naming it "GTS 5-speed". Now the 3-speed C50 Sport was no longer modern, so it was ablished and an entire new model was born, using the previous GTS's four-speed-engine - the CS 50. C(ombinette) S(port) 50! Zundapp stuck to it, still!
Only for internal marketing reasons this was finally renamed to "City-Sport 50", however it was to remain the last of the line, a modernized CS 50 (using a version of the KS 80's engine, doing away with the push-rod gear box but reduced to 50 cc) was the last 50cc Zundapp produced, this was only available in 1984. Zundapp went bankrupt that same year. The production line for the K80 was sold to China and there Xunda-Tianjing continued to build the K80 and a K100 and even a K120 based on the original design, and for a short time even a model with a 90cc four-stroke from Honda (Cub-engine) still under the "Zundapp" brand name. Nowadays production is only continued on a very small scale and "to order" as that factory was taken over by Honda.
Now Zundapp is only kept alive by people like you who restore and ride the old bikes, please, don't let the legend die, every Fury back on the road strengthens the community because the Fury is, in my opinion, as much a Zundapp as one made in Munich/Germany.
With kind regards.
Thanh