The previous message by @franque had me concerned as I really could not remember if the cam gear was removable.
Curiosity got the better of me and I ended up taking the valve cover off this morning to be sure. While there I decided to snap some pics and pay more attention to details.
As can be seen above the cam gear is actually removable
, however, the third lobe that I had originally ignored is now a concern. The lobe seems to have some function in the oiling system, as it has a corresponding spring-loaded pin in the cover that lines up with the oil passages. This can be seen just above the rockers in the following image.
Any guesses as to what this might be? My first thought was a pressure relief or some sort of splash oiling or the cam rollers. The scoring in the cam journals above is hopefully not anything I need to worry about, it doesn't catch my nails and should only really need to hold the outer race for the cam bearings. I checked the bearings to be sure and they still spin freely. One other interesting fact I found was that this engine uses head bolts instead of the seemingly more popular head studs and nuts combo.
The following are two random snaps I took of the cam, one showing the bearing size and the other showing some form of identifying mark. The TY139 designation produces results of the same - or similar - cam on aliexpress but not much else.
Edit: After more digging, it would seem the engine is a TYAN TY150 or a variant thereof. They come with a 49.5mm stroke, 62mm bore and are loosely based on the CB150. Sadly all indicators point to it having a 13mm wrist pin so there are no bigger cylinders that would readily fit. I will confirm all this when I have it apart in a few weeks however at present it seems I would be better served to purchase the 250/230 engine from the bike shown in the post above.
I was also able to tell that the undriven side bearing is a 6203Z.
