Topic: cb550 top end on cb500 bottom?

[73cb500/550]

i have a 73 500 and a 78 550 motor. is it possible to swap the 550 top end on to the 500 bottom. or take the crank out of my 500 and swap it into the 550 motor?
the 550 has a bad crank and im looking to add more power to the 500. i prefer to keep the 500 bottom end if possible.
thanks for the help
chris

[number13]

The answer is yes!
Top ends are interchangeable between
500s and 550s. I believe a smarter member
of this forum said 550 top end parts were sold
as replacement parts after the 500s were discontinued.

Bottom end parts are not interchangeable due to the different
clutch designs.

[Shenanigans]

I hear the 550's have much improved clutch assemblies over the 500's. Might be something to consider.

[TwoTired]

I think the 550 barrels won't fit into the 500 case without some machining.  Otherwise, it's a straightforward swap. ( BrianJ mentioned this when this question came up before.)

[bryanj]

Have heard differing answers on this, some say yes it will fit, the one i tried the lower liners were too big for the holes in the top crancase, but not by much.

Try it without pistons on and see-----you could always have the 500 cylinders bored to take the 550 pistons, then its a real sleeper!!

78 head will fit ok but use 500 inlet stubs and carbs

78 rocker cover is the better as it has the locked rocker spindles

[hymodyne]

the interchangeability of many of the parts on these two engines is a great factor in their operating numbers today.