Topic: cb 100 and cb 125 compatability

[73hutch]

i just got a 72 cb100 to fix up. can anyone tell me if the engine and carbs off of a cb125 are interchangeable?

[kirkn]

Yep. 

If you mean just wholesale swap, yep, they're pretty much interchangeable.  Not all years, tho.  Like a late 70s won't swap for your early 70s without a bit of fabrication.  But, say, a 125 up to about 75 or 76 will slip right in, carb and all.

Kirk

[333]

I'd disagree, Kirkn.  I think they have the same frame through '81.  I had an '80 that I put a '74 center stand on, telling me the frame is the same.

[kirkn]

Mostly.

Around the late 70s, say 78 or 79, the head mount changed from the top of the head to the top-rear, making some fabrication needed.  Also about that time, the carbs changed and the angle was a bit different.  The boot can be stretched to fit, sometimes, but kinda difficult.  And the points moved from the end of the cam to down under the flywheel, necessitating some wiring changes to adapt.  Not impossible any of them, but more than just a drop-in.

Kirk