Originally posted by: KNOWSALOT
MCJ,

As for camshafts, you can use any year model XR200 or XR200R cam EXCEPT for the 1984 and 1985 R versions. These were FRVC engines with two carburetors. Before you get to wondering about the twin carb setup....it's a waste of time and really isn't efficent with such a small engine of a single cylinder design regardless of the mods.

The camshaft that is actually more prefered than the XR200/XR200R cams is the one used in the 1979-1981 XL185S bikes.

As for carburetors, any year model XR200R [other than the 84-85 models ofcourse] will work...but you will find that the one used on the later models [2002 for example] are much cheaper to buy new from Honda than the older models simply because most of the internal parts are now sourced from the US rather than Japan.
The XR carb needs the XR intake to really do any good. However, the XR intake puts the carburetor at a different angle and requires you to make an airboot between the carb and airbox. The intake that was used on the 1984 XR200 [non-R] would bolt up and keep the carb at the correct position, but Honda has also discontiued that part....so unless you find that in a salvage yard....you are left making your airboot for the airbox to carb junction.

Don't worry about swapping heads or valvle springs. Despite the theory that I have read nearly every magazine over the years claim...there is NOT a different porting spec on the XR head compared to the 200X head. In fact, it has the same porting specs as all of the ATC185/200 series cylinder heads.
Same goes for the valve springs. The XR valve springs are not longer and do not have any more sprung tension than the regular engine valve springs have unless the springs are simply worn.

I have recently begun looking into modifications regarding the new series of engines [Brazilian made] used in the CRF150 and CRF230 dirtbikes. Hardly anything is interchangeable regarding a simple bolt-on,.....but I am looking at ways to adapt some of these parts. Mainly the cylinder head. It uses a true bearing instead of the clumsy bushing and also uses a crank trigger igniton rather than the old cam activated pulser system....which really does make a difference in your power onsidering the camshaft is much lighter than the old one...cutting down on recipotating mass. The CRF series also has much larger ports and a larger intake valve.
Converting the cylinder head over isn't much of a deal. Changing the electrical system has been the hard part. Right now, it looks as if I am going to make a new stator cover. If it all turns out to be too much of a hassle for miminum gain with the cylinder alone....I may try an entire engine swap. The entire engine including the electric starter isn't but 2 pounds heavier than the old XR200R engine. Add the weight of a battery and it's looking like the 200X back yard conversions of yesteryear will be making a come back once these CRF230s start to flood the used dirtbike market in a couple of years. I will keep eveyone posted.

Good luck on your project.