Topic: CB550 with a hankering for a 650 head

[CBGhia]

OK.  I have a 550 and I have a spare 650 engine laying around.  I thought about just swapping the whole thing over (and I may still do that) but I also like the idea of the kick starter.  I have read all of the threads that I could find about the hybrids.
I do not want to have to machine the case because I don't want to tear it down that far, so using the 650 pistons and cylinders is out.

I know that the 650 head will bolt up, but the compression will be too low.  I have a set of pistons and cylinders laying here that are 61mm and cut like the Gentlemen's Express.  They have are supposed to increase the stock compression ratio by 1 or so, I think. You can look at the image below...

Will these be enough by themselves to raise the compression?
Or.. Can I deck the head just a bit or deck the cylinders just a bit to bump the compression?

Or should I sell these pistons and just give up the kick starter and run it with the stock 650 engine?

This is a comparison of the stock 650 pistons vs the 61mm (the 650 piston is junk from an old build).

[Justind97]

I have a set of NOS yoshimura pistons for just this build.  You'd have to measure the thickness of the 650 jugs to make sure they are the same.   But if they are, Jugs are already bored, ready to go...

[CBGhia]

I have a set of NOS yoshimura pistons for just this build.  You'd have to measure the thickness of the 650 jugs to make sure they are the same.   But if they are, Jugs are already bored, ready to go...

The cylinders are from a 550 and the pistons are from a 650?  I am a little poor at the moment...

Need a set of 61mm pistons for your 550 then?  Maybe we can work out a trade + cash deal.

[SOHC4 Cafe Racer Fan]

If money is a factor, why not slide the 650 motor in complete.  Are you going to miss the kicker that much?

[Stev-o]

If money is a factor, why not slide the 650 motor in complete. 

+1.  Thought that was the plan already, Joe?

[CBGhia]

If money is a factor, why not slide the 650 motor in complete. 

+1.  Thought that was the plan already, Joe?

Yes, but I starting getting ideas.  It sounds cooler to say you built a hybrid engine.  LOL. 

[turboguzzi]

It sounds cooler to say you built a hybrid engine.  LOL. 
[/quote]

my best bit of advice? build the bike for yourself and not for what others might think of it.

[CBGhia]

It sounds cooler to say you built a hybrid engine.  LOL. 

my best bit of advice? build the bike for yourself and not for what others might think of it.
[/quote]

I built it 7 years ago.  I've just never had electric start on it, and I like the kick start.  I also like the look of the 550 bottom end and I have the pistons sitting here.

I will swap in the 650 engine and sell the pistons. 

[SOHC4 Cafe Racer Fan]

It sounds cooler to say you built a hybrid engine.  LOL. 

my best bit of advice? build the bike for yourself and not for what others might think of it.

I built it 7 years ago.  I've just never had electric start on it, and I like the kick start.  I also like the look of the 550 bottom end and I have the pistons sitting here.

I will swap in the 650 engine and sell the pistons.
[/quote]

I think that's a better idea.  The hybrid requires a bit of machining work.  Who really cares about the look of the kick starter? I suppose if you were out to eliminate every extra ounce (starter motor), it might be a luxury you'd be willing to afford.  The 650 motor mounts up and gives you an instant torque and horsepower boost.  It also incorporates electronic ignition (stock).