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Discussion Starter #1
The mid 70's and later small twins (125-250cc) came in different packages, but looks similar....the CM/Rebels had 2 valve heads, the CB/? had 3 valve heads,
some had 6 speed gearbox. Older CD models had 4 speed, most CM/Rebels had 5 speed?
How much difference is there on these engines? (Will they swap? / Will heads swap? / ...)
 

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Discussion Starter #2
Nobody have insight to the non-balance-axel engines?
 

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Discussion Starter #3
For those who want to know; I have been reading & searching & reading & reading even more...(and; most of the information I found was on the Internet, so it has to be true...):
To get it "out of the way"; the 3 valve / 6-speed / counter-balanced engines (250-400-?) are all different beasts, a later, more refined design from top to bottom.

The CM / CD / CA / CMX / CB-T seems to share all, but bore, stroke (and CD is missing a gear), however the 125 (44mm bore) has more "meat" around the cylinder-bores, so a 185/200/250) cyl (53mm bore) will not fit without work... Having started with numbers; the stroke is 41mm for 125 & 185 cc, 44mm for the 200 cc, and 53mm for the 250 cc
Within the 125 cc - family, there are CM & CB-T, difference; CM has 360° crankshaft -as has all others, exept the (125)CB-T, with it's unique 180° crank...
The CB-T therefore also has a unique camshaft. (and different ignition arrangement).

The most annoying insight, was finding that the early 125 CB-T (77-82+?) had the best camshaft profile of all twins...
 

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Sensei
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We did not get many of those models in the US, so only vaguely familiar........
 

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Discussion Starter #5
Well, the U.S. got the CD, CM & CMX, most probably are 185, 200 & 250 cc , - all are 360° (paralell twins).
There seems to be different cams for CD/CM versus CMX, but without having them in hand, the only difference I have seen is a few degrees change in timing (retarded/advanced) .
 

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Discussion Starter #6 (Edited)
I have been running a twin-carb (Keihin) setup on my CMX250, and think it gives more mid-band power, and snappy response, at a slight mpg disadvantage. I still need to tune / re-jet for top-end performance. (also have opened up the exhaust).
(Carbs, intake-manifolds and filter-adapter from: AliExpress - Online Shopping for Popular Electronics, Fashion, Home & Garden, Toys & Sports, Automobiles and More products - AliExpress , check the carbs that they are marked Keihin, better than the other copies(?)+ K&N filter in the stock box, slightly modified...)
 
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