Topic: cb650 550 swap worth the extra hp and effort?

[nickandkristy02]

here is my question i just recently discovered a 1981 cb650 close by for $200 running with no title. i have read the swap is easy to do. but is it worth the effort and extra hp?.......here is my other issue the po of my bike split the cases and installed new gaskets....but the tranny is not functioning like it should. instead of tearing it apart again should i just throw the 650 in the frame???

[cb650PK]

Is it CV carb motor or slide needle carb motor? On plus side for the 650 motor has primary tensioner. Don't know if the air box from the CV carb motor would fit, if not you have to deal with that.

[nickandkristy02]

thanks for the response but the guy sold it before i got there

[Shadowjack]

I've been considering this as well, but I haven't actually progressed beyond mocking up the engine into a CB500 frame. You can slide the 650 into a 500 frame by removing the sump and the tensioner, although I didn't do the tensioner because I had a bare frame I could lift around it.
The 650 carbs, whether they're mech slides or CV, have a shorter intake passage and sit closer to the head, therefore farther away from the airbox. Plenty of room to get the airbox in there, but it doesn't fit the frame perfectly, and the filter is on the extension and it goes where the battery is on a 500. You'd have to make something work. It helps if you have a complete parts bike to look at.
I should think that there wouldn't be any big showstoppers, just a few little ones, but then, I stopped on this project, temporarily at least.