So, I brought the CB200 home (referenced in another thread viewtopic.php?f=5&t=1193
), and it's in pretty filthy shape. Carbs are black with varnish. Top-end oil leak all over the head... Completely "squared off" back tire, and cupped front tire. Still, it's nothing impossible.
Then, I came across an original Feb '74 Cycle magazine CB200 road test and read:
"Honda's choice of an 18mm carb on the 200 perpetuates a steady decline away from the performance orientation of the CB160. That model had 22mm instruments; the CB175 carbs were 20mm in effective venturi area; now the CB200 is dished up with 18mm gas/air mixers. The rather predictable end result is that the CB200 is effectively strangled at high revs. Compared to the CB200, the CB160 was a racing bike. And with its four speed gearbox, it had to be. We haven't seen any camshsft timing figures on the 200 as yet, but from the feel of the engine, it's a safe bet that the valve timing is more sedate than the CB160 and CB175 as well. Top speed and quarter-mile numbers for our CB200 are almost exactly identical to those of the CB175 tested back in the April '71 issue. It would be very interesting to outfit a CB200 with the carbs from a CB160 and the camshaft and exhaust system from a CB175."
Then, I came across the Megacycle cam catalog, and they offer two "better" cams for the CB200 - a "mid-range" and a "road race" profile. Road race requires special springs and pistons, but the mid-range is described as working with stock springs and pistons.
I happen to have an old SL125 motor, and it has the Keihin 22mm carb on it. Other than being a bit larger, it looks identical to the CB200's Keihin 20 carb. The 22 is cast "22" on the lid, and the slide is indeed 22mm diameter. The 20 carb is cast "20" on the lid, but the slide is only 18mm in diameter.
The intake manifold throat on the CB200 is about 2mm in diameter larger at the carb flange than the carb. When bolted together and viewed looking thru the manifold back at the carb, the carb has a 1mm overhang all 'round. The intake manifold tapers to even larger diameter towards the head.
Looking down the port into the head, there's lots of casting bumps, flash and flaws all the way down that port. I've done some porting on the old SL125 head (because it has the same flaws, stock) and there's lots of room for improvement. Very easy, too.
Hmmm..... has anyone ever pulled all this together into a little hot-rod 200? Wonder if it would be worth the effort. Probably not, but is sure is fun to kick it around... Those 22mm carbs are probably a dime-a-dozen on ebay and look to be completely interchangeable onto the 200. Do a little port matching, and jetting, a little freer breathing on the exhaust and you'd probably have a machine that's almost as strong as a stock Honda 250 Nighthawk... :lol: